underbridge

As a noun underbridge

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

As an adjective undefined is

lacking a definition or value.

As nouns the difference between underbridge and dog

is that underbridge is (british) a bridge that allows traffic to pass under a road, river, railway etc while dog is a mammal, canis lupus familiaris , that has been domesticated for thousands of years, of highly variable appearance due to human breeding.

As a verb dog is

to pursue with the intent to catch.

As nouns the difference between underbridge and null

is that underbridge is a bridge that allows traffic to pass under a road, river, railway etc while null is a non-existent or empty value or set of values.

As an adjective null is

having no validity, "null and void.

As a verb null is

to nullify; to annul.

As nouns the difference between underbridge and tunnel

is that underbridge is a bridge that allows traffic to pass under a road, river, railway etc while tunnel is an underground or underwater passage.

As a verb tunnel is

to make a tunnel through or under something, to burrow.

As nouns the difference between underbridge and underpass

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