to open the mouth somewhat involuntarily with a prolonged, deep inhalation and sighing or heavy exhalation, as from drowsiness or boredom.

to open wide like a mouth.

to extend or stretch wide, as an open and deep space.

to say with a yawn.

Archaic . to open wide, or lay open, as if by yawning.

an act or instance of yawning.

an opening; open space; chasm.

Also, yawner. Informal . something so boring as to make one yawn

Critics say the new fashions are one big yawn.

verb

fatigue catch flies , divide , doze , drowse , expand , gap , gape , give , nap , part , sleep , snooze , spread , yaw , yawp * , bore , cavity , chasm , dehisce , open , opening , oscitate , tedium