Definition of "demon"

An evil supernatural spirit.

1. An evil spirit resident in or working for Hell; a devil.  quotations  examples

   Quotations

   • So what does the Gospel of Judas really say? It says that Judas is a specific demon called the "Thirteenth." In certain Gnostic traditions, this is the given name of the king of demons - an entity known as Ialdabaoth who lives in the 13th realm above the earth. Judas is his human alter ego, his undercover agent in the world. These Gnostics equated Ialdabaoth with the Hebrew Yahweh, whom they saw as a jealous and wrathful deity and an opponent of the supreme God whom Jesus came to earth to reveal.Whoever wrote the Gospel of Judas was a harsh critic of mainstream Christianity and its rituals. Because Judas is a demon working for Ialdabaoth, the author believed, when Judas sacrifices Jesus he does so to the demons, not to the supreme God. This mocks mainstream Christians' belief in the atoning value of Jesus' death and in the effectiveness of the Eucharist.

     2007 December 2, April D. DeConick, “What the Gospel of Judas really says”, in The New York Times‎, archived from the original on 23 November 2011, Essay‎

2. (now chiefly historical) A false god or idol; a Satanic divinity.

3. A very wicked or malevolent person; also (in weakened sense) a mischievous person, especially a child.  examples

4. A source (especially personified) of great evil or wickedness; a destructive feeling or character flaw.  examples

5. (in the plural) A person's fears or anxieties.  quotations  examples

   Quotations

   • After a short spell on an adult psychiatric ward, she decided to find her own way to deal with her demons.

     2013 January 21, The Guardian

A neutral supernatural spirit.

1. A person's inner spirit or genius; a guiding or creative impulse.  quotations  examples

   Quotations

   • Oh Anthony […] Thy Dæmon that thy spirit which keepes thee, is Noble, Couragious, high vnmatchable.

     c. 1606–1607, William Shakespeare, “The Tragedie of Anthonie and Cleopatra”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act II, scene iii]

   • “You saw her. And I picked her up,” Lyra said, blushing, because of course it was a gross violation of manners to touch something so private as someone else's dæmon.

     2000, Phillip Pullman, The Amber Spyglass

2. (Greek mythology) A tutelary deity or spirit intermediate between the major Olympian gods and mankind, especially a deified hero or the entity which supposedly guided Socrates, telling him what not to do.

3. A spirit not considered to be inherently evil; a (non-Christian) deity or supernatural being.  examples

4. A hypothetical entity with special abilities postulated for the sake of a thought experiment in philosophy or physics.  quotations  examples

   Quotations

   • Let the orders now be that each demon is to stop all molecules from crossing his area in either direction except 100 coming from A, arbitrarily chosen to be let pass into B, and a greater number, having among them less energy but equal momentum, to cross from B to A.

     1874, William Thomson, 1st Baron Kelvin, “Kinetic Theory of the Dissipation of Energy” in Nature 9, 441-444

Someone with great strength, passion or skill for a particular activity, pursuit etc.; an enthusiast.  quotations  examples

(card games) A type of patience or solitaire (card game) played in the UK and/or US.  quotations  examples

Any of various hesperiid butterflies of the genera Notocrypta and Udaspes.  examples

(physics) Acronym of distinct electron motion particle: A quasiparticle, a type of massless neutral electron excitation associated with superconductivity.  examples

(computing) Alternative spelling of daemon  examples