WordNet records no synonym and no antonym for khyber pass. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a mountain pass of great strategic and commercial value in the Hindu Kush on the border between northern Pakistan and western Afghanistan; a route by which invaders entered India
Synonyms, antonyms and the broader and narrower relations for khyber pass come from Princeton University’s WordNet. Full sources and licences.