1. a voiceless fricative sound like that of a prolonged s
2. such a sound uttered as an exclamation of derision, contempt, etc., especially by an audience or crowd
3. electronics receiver noise with a continuous spectrum, caused by thermal agitation, shot noise, etc.
4. ( intr) to produce or utter a hiss
5. ( trans) to express with a hiss, usually to indicate derision or anger