Nouns

(n)yawn, yawning, oscitance, oscitancyan involuntary intake of breath through a wide open mouth; usually triggered by fatigue or boredom“he could not suppress a yawn”, “the yawning in the audience told him it was time to stop”, “he apologized for his oscitancy”

Adjectives

(s)yawninggaping open as if threatening to engulf someone or something“the yawning mine shaft”, “a yawning abyss”
(s)yawningwith the mouth wide open indicating boredom or sleepiness“a yawning congregation”
(s)drowsy, oscitant, yawningshowing lack of attention or boredom“the yawning congregation”