(1):

(a.) To lower the pitch of; to cause to sound less sharp; to let fall from the pitch.

(2):

(v. i.) To become or grow flat, even, depressed dull, vapid, spiritless, or depressed below pitch.

(3):

(a.) To reduce to an even surface or one approaching evenness; to make flat; to level; to make plane.

(4):

(a.) To make vapid or insipid; to render stale.

(5):

(a.) To throw down; to bring to the ground; to prostrate; hence, to depress; to deject; to dispirit.