Crossword puzzle clue "expresses stern disapproval of"

REBUKE, to reprove sternly

BOO, to show disapproval by making this sound, also BOOH

HARRUMPH, to clear one's throat noisily in annoyance, also HARUMPH

HOOT, to cry like an owl, also HOUT, WHOOT

PSHAW, to utter an expression of contempt or disapproval