Flatten

1. To become or grow flat, even, depressed dull, vapid, spiritless, or depressed below pitch.
2. To throw down; to bring to the ground; to prostrate; hence, to depress; to deject; to dispirit.
3. To lower the pitch of; to cause to sound less sharp; to let fall from the pitch.
4. To reduce to an even surface or one approaching evenness; to make flat; to level; to make plane.
5. To make vapid or insipid; to render stale.