sib·i·late verb alsosib·il·late\ˈsibəˌlāt\ (-ed/-ing/-s) Etymology: Latin sibilatus, past participle of sibilare to hiss, whistle intransitive verb 1.: hiss 2.: to utter an initial sibilant : prefix an \s\-sound transitive verb 1.: hiss 2.: to pronounce with an initial sibilant : prefix an \s\-sound to