WordNet records no synonym and no antonym for huckleberry. 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.
any of various dark-fruited as distinguished from blue-fruited blueberries
any of several shrubs of the genus Gaylussacia bearing small berries resembling blueberries
blue-black berry similar to blueberries and bilberries of the eastern United States
Synonyms, antonyms and the broader and narrower relations for huckleberry come from Princeton University’s WordNet. Full sources and licences.