A Crack

1. A thin and usually jagged space opened in a previously solid material.
2. A large crack had formed in the roadway.
3. A narrow opening.
4. A sharply humorous comment; a wisecrack.
5. A potent, relatively cheap, addictive variety of cocaine; often a rock, usually smoked through a crack-pipe.
6. (onomatopoeia) The sharp sound made when solid material breaks.
7. (onomatopoeia) Any sharp sound.
8. (informal) An attempt at something.
9. (vulgar, slang) Vagina.
10. (informal) The space between the buttocks.
11. (Northern England, Scotland, Ireland) Conviviality; fun; good conversation, chat, gossip, or humorous storytelling; good company.
12. (Northern England, Scotland, Ireland) Business; events; news.
13. (computing) A program or procedure designed to circumvent restrictions or usage limits on software.
14. (Cumbria, elsewhere throughout the North of the UK) a meaningful chat.
15. (Internet slang) Extremely silly, absurd or off-the-wall ideas or prose.
16. The tone of voice when changed at puberty.
17. (archaic) A mental flaw; a touch of craziness; partial insanity.
18. (archaic) A crazy or crack-brained person.
19. (obsolete) A boast; boasting.
20. (obsolete) Breach of chastity.
21. (obsolete) A boy, generally a pert, lively boy.
22. (slang, dated, Britain) A brief time; an instant; a jiffy.

(Scots language, common in lowland Scotland and Ulster, conviviality): In the last few decades the word has been adopted into Gaelic; as there is no "k" in the Irish language the spelling craic has been devised.

(vulgar: space between the buttocks): bum crack (UK), arse crack (UK), ass crack (US)

(cocaine that is heat-altered at the moment of inhalation): crack cocaine

(A crazy or crack-brained person): crackpot