Flāt'ten1, v. t.
(flāt'tn), v. t. [imp. & p. p. FLATTENED; p. pr. & vb. n. FLATTENING.] [From flat, q. v.]
Sense 1. To reduce to an equal or even surface; to level; to make flat.
Sense 2. To throw down; to bring to the ground; to prostrate; hence, to depress; to deject; to dispirit.
Sense 3. To make vapid or insipid; to render stale.
Sense 4. (Mus.) To lower the pitch of; to cause to sound less sharp; to let fall from the pitch.
To flatten a sail (Naut.), to extend a sail lengthwise of the vessel, so that its effect is only lateral. Brande.