Crack is a versatile English word with multiple meanings:
1. As a noun: a narrow opening or fissure ("There's a crack in the wall")
2. As a verb: to break without complete separation ("Don't crack your phone screen!")
3. As a noun: a sharp sound ("We heard a loud crack of thunder")
4. As a noun: a highly addictive form of cocaine
5. As an adjective: excellent or first-rate ("He's a crack shot with a rifle")
6. As a verb: to solve a difficult problem ("The detective cracked the case")