overbridge

As a noun overbridge

is (british) a bridge that allows traffic to pass over a road, river, railway etc.

As an adjective undefined is

lacking a definition or value.

In british terms the difference between flyover and overbridge

is that flyover is a road or railway that passes over another, allowing routes to cross without interruption while overbridge is a bridge that allows traffic to pass over a road, river, railway etc.

As nouns the difference between flyover and overbridge

is that flyover is a low-level flight, especially of military aircraft, of a ceremonial nature; a flypast British while overbridge is a bridge that allows traffic to pass over a road, river, railway etc.

As nouns the difference between overbridge and underpass

is that overbridge is a bridge that allows traffic to pass over a road, river, railway etc while underpass is a road or a pedestrian passage in a tunnel that runs underneath a road or railroad.