unioid adjective 1noun 1forms 3 adjective1 •(rare) Resembling or characteristic of the unios. noun1 •(rare) Synonym of unionoid.Species of the oldest freshwater bivalve genus, the unioid Archanodon, are well known from Frasnian strata in New York State (Bridge et al. 1986). — 1996 formsunioids · more unioid · most unioid
