Answer: hissed

AnswerCrossword Clue
HISSED

Made a whistling sound

HISSED

Clearly wasn't pleased

HISSED

Warned, snake-style

HISSED
Gave the villain his due
HISSED
Greeted the villain
HISSEDMade sibilant sounds
HISSEDBlew off steam?
HISSEDShowed displeasure
HISSEDMade an ophidian sound
HISSEDMade like an asp
HISSEDHeckled
HISSEDRazzed the villain
HISSEDExpressed disapproval.
HISSEDShowed disapproval.
HISSEDGreeted the villain.
HISSEDLet off steam.
HISSEDDisapproved vocally.
HISSEDCompanion of booed
HISSEDShowed disapproval
HISSEDSounded like a snake
HISSEDSounded angry
HISSEDDisplayed displeasure
HISSEDRazzed
HISSEDGreeted the bad guy, maybe