LINE [C] › a line on the surface of something that is damaged: Several cups had cracks in them. NARROW SPACE [C] › a narrow space between two parts of something or between two things: I could see sunlight through a crack in the curtains. DRUG [U] › an illegal drug that is very harmful NOISE [C] › a sudden, short noise: a crack of thunder JOKE [C] › an unkind joke or remark: He was always making cracks about my weight. have/take a crack at sth informal › to try to do something: I've never put up shelves before, but I'll have a crack at it.