sizz(noun, verb) noun1. (rare or archaic) fizz verb1. express or utter with a hissSimilar word(s): hiss, sibilate, sissDefinition categories: communication, mouth, speak, talk, utter, verbalise, verbalize2. make a sharp hissing sound, as if to show disapprovalSimilar word(s): hiss, sibilate, sissDefinition categories: communication, emit, utter