WordNet records no synonym and no antonym for bifurcation. It is the only member of each of its synsets, 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 bifurcating branch (one or both of them)
the place where something divides into two branches
the act of splitting into two branches
Synonyms, antonyms and the broader and narrower relations for bifurcation come from Princeton University’s WordNet. Full sources and licences.