1. pronunciation with a sibilant (hissing or whistling) sound • Syn: assibilation • Derivationally related forms: assibilate (for: assibilation), sibilate • Hypernyms: pronunciation 2. a fricative sound (especially as an expression of disapproval) - the performers could not be heard over the hissing of the audience • Syn: hiss, hissing, hushing, fizzle • Derivationally related forms: sibilate, hiss (for: hissing), hiss (for: hiss) • Hypernyms: noise