Answer: boohiss

AnswerCrossword Clue
BOOHISS[I disapprove]
BOOHISSDispleased spectator's cry
BOOHISSCompound cry of displeasure
BOOHISSAudience disapproval
BOOHISSAccompanier of a thrown tomato
BOOHISS"That's terrible!"
BOOHISSExpression of disapproval