1. adjective /ˈsɪb.ɪ.lənt/
Characterized by a hissing sound such as the "s" or "sh" in sash or surge.
She had a curious habit of prefacing everything she said with a soft sibilant sound."S-s-s Grace," she said, "its just like I was telling Brother Hutson the other day. S-s-s Brother Hutson, I said, looks like were fighting a losing battle, a losing battle. I said."
2. noun /ˈsɪb.ɪ.lənt/
A hissing sound such as the s or sh in sash or surge.
Groove fricatives all have more or less of an [s]-like quality, and are for this reason sometimes called sibilants.
Wikipedia foundation.