An unbridgeable gap or divide between two sides in an argument is so great that the two sides seem unlikely ever to agree. the apparently unbridgeable gulf between the SIS and the Security Service The gap between the President and his opponents is unbridgeable. unbridgeable differences between two people, groups, or ideas are so big that no one will ever agree about them or be satisfied with them unbridgeable gulf/gap/chasm etc (between sb/sth and sb/sth)