A bascule bridge is a moveable bridge with a counterweight that continuously balances a span, or leaf, throughout its upward swing to provide clearance for boat traffic. It may be single- or double-leafed.

A moveable bridge, or movable bridge, is a bridge that moves to allow passage for boats or barges. In American English, the term is synonymous with drawbridge, and the latter is the common term, but drawbridge can be limited to the narrower, historical definition used in some other forms of English, in which drawbridge refers to only a specific type of moveable bridge often found in castles.