flat•tenPronunciation: (flat'n), [key]
to make flat.
to knock down: The boxer flattened his opponent in the second round.
to become flat.
2. flatten in, Naut.
See flat 1
3. flatten out, Aeron.
to fly into a horizontal position, as after a dive.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.