희박해요 · 희박했어요 · 희박한 (+noun)
thin, sparse; slim, faint (chance)
Example
산꼭대기는 공기가 희박해서 숨쉬기가 힘들어요.
At the mountaintop the air is thin, so it's hard to breathe.
Word parts
희 rare+박 thin
Literally 'rare and thin'.
Good to know
Classic collocation: 가능성이 희박하다 'the chances are slim'.