hisssssss

When my brother and I would tick my mother off, but we were in public so she couldn't "snatch us bald" (a pet threat that she never made good on), she would usually handle it with The Look. The Look was bad. The Look meant business. The Look worked 98% of the time.

The remaining 2% of the time, she resorted to a kind of whispered/hissed admonition, heavy with implied doom. However, on those few occasions that she did, it was very effective.

Sssssit down NOW! And husssssssssssssh! Zip it! I sssssaid ZIP IT!

sibilate
verb

1. To utter or pronounce with a hissing sound.
2. To make a sharp sibilant sound

Synonyms: fizz, fizzle, hiss, sizzle, swish, whiz, whoosh