sibilant (adj.) Look up sibilant at Dictionary.com
1660s, from Latin sibilantem (nominative sibilans), present participle of sibilare "to hiss, whistle," possibly of imitative origin (compare Greek sizein "to hiss," Lettish sikt "to hiss," Old Church Slavonic svistati "to hiss, whistle"). Related: Sibilance; sibilation (1620s).