I. sib ‧ ilant 1 /ˈsɪbələnt, ˈsɪbɪlənt/ BrE AmE adjective formal
[ Date: 1600-1700 ; Language: Latin ; Origin: present participle of sibilare 'to hiss, whistle' ]
making or being an ‘s’ or ‘sh’ sound:
a sibilant whisper
II. sibilant 2 BrE AmE noun [countable] technical
a sibilant sound such as ‘s’ or ‘sh’ in English