sibilantPronunciation: /ˈsɪbɪl(ə)nt/Definition of sibilant adjective 1making or characterized by a hissing sound:his sibilant whisper 2 Phonetics (of a speech sound) sounded with a hissing effect, for example s, sh. noun Phonetics a sibilant speech sound. Derivatives sibilance noun sibilantly adverb Origin: mid 17th century: from Latin sibilant- 'hissing', from the verb sibilaresibilant in other Oxford dictionaries Definition of sibilant in the US English dictionary