To sibilate is to say something with a hissing sound, just like the librarian who shushes you when you’re speaking too loudly during your study session. (How many sibilant sounds can you count in the previous sentence?) “Sibilate” comes directly from the Latin root “sibilare,” meaning “to hiss or whistle.” “Hiss” is the onomatopoeia for the sound snakes make when they are warning away predators. If you have a pet snake, an exotic pet veterinarian says you may never hear it sibilate, because it doesn’t feel danger; however, snakes in the wild sibilate often in uncertain or dangerous situations.