Longman Dictionary of Contemporary English
Wiktionary
a. Unable to be bridged or crossed; impossible to span. alt. Unable to be bridged or crossed; impossible to span.
WordNet
adj. not bridgeable; "a wide unbridgeable river"; "unbridgeable generation gap" [ant: bridgeable]
Usage examples of "unbridgeable".
Lun and Phari ridges both run south, the gap between them widening to unbridgeable distances south of the cableway we have just crossed.
Ego and Eco were still staring at each other across an unbridgeable gulf, and the two absolutisms were altogether incompatible.
From Chomo Lori, the K'un Lun and Phari ridges both run south, the gap between them widening to unbridgeable distances south of the cableway we have just crossed.
But the lesson had been brought home when, in the course of a conversation, they found themselves separated by a sudden, unbridgeable gap-Jacob had told a story about Earth's old class struggles that Culla failed to understand.
What looked like a vast, unbridgeable gulf between the life sciences and the physical sciences is shrinking so fast that it's turning out to be little more than a thin line scratched in the sand of the scientific desert.