a bell tower, either attached to a church or other building or standing apart.

the part of a steeple or other structure in which a bell is hung.

a frame of timberwork that holds or encloses a bell.

Slang . head; mind

a belfry full of curious notions.

have bats in one's belfry. bat 2 ( def. 3 ) .

noun

bell tower , campanile , carillon , clocher , cupola , dome , head , minaret , spire , steeple , turret , bell-tower , tower