FLAT'TEN, v.t. flat'n.1. To make flat; to reduce to an equal or even surface; to level.2. To beat down to the ground; to lay flat.3. To make vapid or insipid; to render stale.4. To depress; to deject, as the spirits; to dispirit.5. In music, to reduce, as sound; to render less acute or sharp.
FLAT'TEN, v.i. flat'n. 1. To grow or become even on the surface.2. To become dead, stale, vapid or tasteless.3. To become dull or spiritless.