flatten

verb flattens · flattening · flattened

1. transitive To make something flat or flatter. As there was a lot of damage, we chose the heavy roller to flatten the pitch.
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. 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.
3. transitive To knock down or lay low. The prize fighter quickly flattened his challenger.
4. intransitive To become flat or flatter; to plateau. Prices have flattened out.
5. intransitive To be knocked down or laid low.
6. To lower by a semitone.
7. To make vapid or insipid; to render stale.
8. 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. transitive To combine (separate layers) into a single image.