Crossword clue: an involuntary intake of breath through a wide open mouth; usually triggered by fatigue or boredom

The most common answer is yawn (4 letters).

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

Possible answers

yawn 4 letters wn-def

utter a yawn, as from lack of oxygen or when one is tired

yawning 7 letters wn-def

an involuntary intake of breath through a wide open mouth; usually triggered by fatigue or boredom