Definition of "open"

open¹

/ˈəʊp(ə)n/

adjective
comparative more open, superlative most open
1. (usually not comparable) Not closed.
  1. Able to be accessed (physically).
  2. Able to have something pass through or along it.
    Quotations
    The open road, the dusty highway […]
    1908 October, Kenneth Grahame, The Wind in the Willows, New York, N.Y.: Charles Scribner’s Sons
  3. (of a body part) Not covered; showing what is inside.
  4. (of a sandwich, etc.) Composed of a single slice of bread with a topping.
    Quotations
    Starry food is fun to make. You can buy bright yellow American mustard (which isn’t too strong!) in squeezy bottles and pipe stars on to hot dogs and open burgers or sandwiches.
    2001, Jennie Walters, Caz’s Birthday Blues (Party Girls)‎, London: Hodder Children’s Books
    When the burgers are ready, place them on the toasted rolls with the romaine lettuce leaves and top with the salsa. Serve as open burgers.
    2012, Jo McAuley, “[Meat and Poultry] Turkey Burgers with Spicy Salsa”, in Hamlyn QuickCook: Low Fat, London: Hamlyn, page 152
    Sunday morning in Wellow and we feast on open bagels with grilled ham, tomato and Swiss cheese, requested and highly praised.
    2015, Michael Robotham, chapter 17, in Close Your Eyes, London: Sphere, page 133
2. Not physically drawn together, closed, folded or contracted; extended.
  Quotations
  Each, with open arms, embraced her chosen knight.
  1700, [John] Dryden, “The Flower and the Leaf: Or, The Lady in the Arbour. A Vision.”, in Fables Ancient and Modern; […], London: […] Jacob Tonson, […]
3. (not comparable) Actively conducting or prepared to conduct business.
  Quotations
  Since the launch early last year of […] two Silicon Valley start-ups offering free education through MOOCs, massive open online courses, the ivory towers of academia have been shaken to their foundations. University brands built in some cases over centuries have been forced to contemplate the possibility that information technology will rapidly make their existing business model obsolete.
  2013 July 20, “The attack of the MOOCs”, in The Economist, volume 408, number 8845
4. (comparable) Receptive.
  Quotations
  Wherefore if Demetrius […] have a matter against any man, the law is open and there are deputies.
  1611, The Holy Bible, […] (King James Version), London: […] Robert Barker, […], Acts 19:38
  The service that I truly did his life, / Hath left me open to all injuries.
  c. 1596–1599 (date written), William Shakespeare, “The Second Part of Henry the Fourth, […]”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act V, scene ii]
  When the top sheet, blanket, and bedspread of a closed bed are turned back, or fanfolded, the closed bed becomes an open bed, or a bed ready to receive a patient or resident.
  2005, Pamela J. Carter, Susan Lewsen, Lippincott's Textbook for Nursing Assistants, page 277
  A U.K. survey found attitudes toward public transit had been set back by two decades, with only 43% of drivers open to using their car less, even if public transport improves.
  2021 April 2, Ciara Nugent, “Can Public Transit Survive the Pandemic? London's New Transport Commissioner Wants You to Believe It Can”, in Time‎
5. (not comparable) Public
  Quotations
  His thefts were too open.
  c. 1597 (date written), William Shakespeare, “The Merry Wiues of Windsor”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene iii]
  That I may find him, and with secret gaze / Or open admiration him behold.
  1667, John Milton, “Book III”, in Paradise Lost. […], London: […] [Samuel Simmons], […]; republished as Paradise Lost in Ten Books: […], London: Basil Montagu Pickering […], 1873,
  Due to severe and pervasive discrimination, people dared not be open about their homosexuality, and because no one would be open, social prejudice and discrimination became even stronger.
  2001, Xiaopei He, “Chinese Queer (Tongzhi) Women Organizing in the 1990s”, in Ping-Chun Hsiung, Maria Jaschok, Cecilia Milwertz, Red Chan, editors, Chinese Women Organizing: Cadres, Feminists, Muslims, Queers‎, Berg, page 41
6. (not comparable) With open access, of open science, or both.
7. (not comparable) Candid, ingenuous, not subtle in character.
  Quotations
  with aspect open, shall erect his head
  1731-1735, Alexander Pope, Moral Essays
  The Moor is of a free and open nature.
  c. 1603–1604 (date written), William Shakespeare, “The Tragedie of Othello, the Moore of Venice”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene iii]
  The French are always open, familiar, and talkative.
  1705, J[oseph] Addison, Remarks on Several Parts of Italy, &c. in the Years 1701, 1702, 1703, London: […] Jacob Tonson, […]
8. (now regional) Mild (of the weather); free from frost or snow.
  Quotations
  He desires me to tell you that the present open weather induces him to accept Mr Vernon's invitation to prolong his stay in Sussex that they may have some hunting together.
  c. 1794, Jane Austen, Lady Susan
9. (mathematics, logic, of a formula) Having a free variable.
10. (mathematics, topology, of a set) Which is part of a predefined collection of subsets of X , that defines a topological space on X .
11. (graph theory, of a walk) Whose first and last vertices are different.
12. (computing, not comparable, of a file, document, etc.) In current use; connected to as a resource.
13. (engineering, gas and liquid flow, of valve or damper) To be in a position allowing fluid to flow.
14. (electricity, of a switch or circuit breaker) To be in a position preventing electricity from flowing.
15. (sometimes business) Not fulfilled or resolved; incomplete.
16. Not settled or adjusted; not decided or determined; not closed or withdrawn from consideration.
17. (music, stringed instruments) Of a note, played without pressing the string against the fingerboard.
18. (music) Of a note, played without closing any finger-hole, key or valve.
19. Not of a quality to prevent communication, as by closing waterways, blocking roads, etc.; hence, not frosty or inclement; mild; used of the weather or the climate.
20. (law, of correspondence) Written or sent with the intention that it may made public or referred to at any trial, rather than by way of confidential private negotiation for a settlement.
21. (phonetics) Uttered with a relatively wide opening of the articulating organs; said of vowels.
  Quotations
  "Supposing somebody sees you, with all those flowers too? Supposing somebody writes him a letter? Ooooh!" (a pure round open Tamil O.)
  1959, Anthony Burgess, Beds in the East (The Malayan Trilogy), published 1972, page 421
22. (phonetics) Uttered, as a consonant, with the oral passage simply narrowed without closure.
23. (phonetics, of a syllable) That ends in a vowel; not having a coda.
24. (computing, education) Made public, usable with a free licence and without proprietary components.
25. (medicine) Resulting from an incision, puncture or any other process by which the skin no longer protects an internal part of the body.
26. (computing, used before "code") Source code of a computer program that is not within the text of a macro being generated.
27. (of a multi-word compound) Having component words separated by spaces, as opposed to being joined together or hyphenated; for example, time slot as opposed to timeslot or time-slot.

open²

/ˈəʊp(ə)n/

verb
third-person singular simple present opens, present participle opening, simple past and past participle opened
1. (transitive) To make something accessible or allow for passage by moving from a shut position.
  Quotations
  I made a speaking trumpet of my hands and commenced to whoop “Ahoy!” and “Hello!” at the top of my lungs. […] The Colonel woke up, and, after asking what in brimstone was the matter, opened his mouth and roared “Hi!” and “Hello!” like the bull of Bashan.
  1913, Joseph C. Lincoln, chapter 7, in Mr. Pratt's Patients
  ‘No. I only opened the door a foot and put my head in. The street lamps shine into that room. I could see him. He was all right. Sleeping like a great grampus. Poor, poor chap.’
  1963, Margery Allingham, chapter 20, in The China Governess‎
2. (transitive) To make (an open space, etc.) by clearing away an obstacle or obstacles, in order to allow for passage, access, or visibility.
  Quotations
  He had kept on recording everything then, when he had been sure he was going to die, and he went on recording everything now, when he was suddenly consumed with hate for the boy in his arms and overwhelmed by a desire to put something—his motorcycle key would do nicely — into the interfering little prayboy’s throat and open him like a can of beer.
  1996, Stephen King, Desperation
3. (transitive, intransitive, engineering, gas and liquid flow, of valve or damper) To move to a position allowing fluid to flow.
4. (transitive, intransitive, electricity, of a switch, fuse or circuit breaker) To move to a position preventing electricity from flowing.
5. (Manglish, Philippines) To turn on; to switch on.
6. (transitive) To bring up, broach.
7. (transitive) To enter upon, begin.
8. (transitive) To spread; to expand into an open or loose position.
9. (transitive) To make accessible to customers or clients.
  Quotations
  Suiping was opened as a main station in 1912 when Rev. H. M. Nesse arrived to take charge of the mission work.
  1934, White Unto Harvest in China: A Survey of the Lutheran United Mission, the China Mission of the N.L.C.A., 1890-1934‎, page 76
10. (transitive) To start (a campaign).
11. (intransitive) To become open.
  Quotations
  I stumbled along through the young pines and huckleberry bushes. Pretty soon I struck into a sort of path that, I cal'lated, might lead to the road I was hunting for. It twisted and turned, and, the first thing I knew, made a sudden bend around a bunch of bayberry scrub and opened out into a big clear space like a lawn.
  1913, Joseph C. Lincoln, chapter 1, in Mr. Pratt's Patients
12. (intransitive) To begin conducting business.
13. (intransitive, cricket) To begin a side's innings as one of the first two batsmen.
14. (intransitive, poker) To bet before any other player has in a particular betting round in a game of poker.
15. (transitive, intransitive, poker) To reveal one's hand.
16. (computing, transitive, intransitive) To connect to a resource (a file, document, etc.) for viewing or editing.
17. (transitive, nursing) To make (a bed) ready for a patient by folding back the bedcovers.
  Quotations
  Follow agency policy, or open the bed by folding the top linens back.
  2013, Susan C. deWit, Patricia A. Williams, Fundamental Concepts and Skills for Nursing, page 318
18. (obsolete) To disclose; to reveal; to interpret; to explain.
  Quotations
  The king opened himself to some of his council, that he was sorry for the earl's death.
  1622, Francis Bacon, The History of the Reign of King Henry the Seventh
  Unto thee have I opened my cause.
  1611, The Holy Bible, […] (King James Version), London: […] Robert Barker, […], Jeremiah 20:12

open³

/ˈəʊp(ə)n/

noun
plural opens
1. (in the definite) Open or unobstructed space; an exposed location.
2. (in the definite) Public knowledge or scrutiny; full view.
3. (electronics) A defect in an electrical circuit preventing current from flowing.
4. A sports event in which anybody can compete.
5. The act of something being opened, such as an e-mail message.
  Quotations
  The total number of opens from original, or unique, subscribers.
  2016, Ian Dodson, The Art of Digital Marketing, page 144

Definition of "open"

open1

adjective

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open2

verb

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open3

noun

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open¹

open²

open³