stuffy; close; lacking air circulation

bored; depressed; in low spirits; melancholy

muffled; low and deep (of sound)

to stay in a place for a long time (especially indoors)

to cover tightly; to seal; to smother (e.g., when cooking)

to keep one's feelings or words to oneself; to hide in one's heart

sealed; airtight; closed up (of a vehicle or container)

an unhappy mood; worries; boredom (often as a noun)