Definition of "flatten"

flatten

/ˈflætən/

verb
third-person singular simple present flattens, present participle flattening, simple past and past participle flattened
1. (transitive) To make something flat or flatter.
2. (reflexive) To press one's body tightly against a surface, such as a wall or floor, especially in order to avoid being seen or harmed.
  Quotations
  With a bolt of fright he remembered that there was no bathroom in the Hob-house Room. He leapt along the corridor in a panic, stopping by the long-case clock at the end where he flattened himself against the wall.
  1994, Stephen Fry, chapter 2, in The Hippopotamus
3. (transitive) To knock down or lay low.
4. (intransitive) To become flat or flatter; to plateau.
5. (intransitive) To be knocked down or laid low.
6. (music) To lower by a semitone.
7. To make vapid or insipid; to render stale.
8. (programming, transitive) To reduce (a data structure) to one that has fewer dimensions, e.g. a 2×2 array into a list of four elements.
9. (computer graphics, transitive) To combine (separate layers) into a single image.