凹

to lose heart; to be discouraged; to be dejected; to be exhausted; to be tired out

odd couple; incongruous couple

concave lens

intaglio printing

to dent; to indent; to depress; to humiliate

Geometry

concave polygon; non-convex polygon

plano-concave lens

Printing

copperplate engraving

Psychology

developmental irregularities; developmental disorder; neurodiversity

Work of art, literature, music, etc. name

Africa Scream (film)

Rare term

to cave in; to become depressed; to sink

Rare term

hollow; pond in a hollow

Proverb; Rare term

when the right conditions are fulfilled, things will turn out well on their own; a sunken place will collect water

Proverb; Rare term

someone in bad circumstances will continue to accumulate difficulties

hollow; cavity; sunken place

Archaic

vagina; female genitalia