Definition of hisses:
(v) :
(intransitive) To make a hiss, a sibilant sound of air escaping.
(n) :
A sibilant sound, such as that made by a snake or escaping steam; an unvoiced fricative.
(n) :
An expression of disapproval made using such a sound.
(v) :
(transitive, intransitive) To condemn or express contempt (for someone or something) by hissing.
(v) :
(transitive) To utter (something) with a hissing sound.
(v) :
(transitive) To call someone by hissing.