(1):

(n.) A room in a tower in which a bell is or may be hung; or a cupola or turret for the same purpose.

(2):

(n.) A bell tower, usually attached to a church or other building, but sometimes separate; a campanile.

(3):

(n.) The framing on which a bell is suspended.

(4):

(n.) A movable tower erected by besiegers for purposes of attack and defense.