crack ‧ er /ˈkrækə $ -ər/ BrE AmE noun [countable]
1 . a hard dry type of bread in small flat shapes, that is often eaten with cheese
2 . ( also Christmas cracker ) a decorated paper tube that makes a small exploding sound when you pull it apart. Crackers contain a small gift, a paper hat, and a joke, and are used at Christmas in Britain.
3 . a ↑ firecracker
4 . British English spoken something that is very good or funny:
That was a cracker of a goal.
5 . someone who illegally breaks into a computer system in order to steal information or stop the system from working properly SYN hacker :
computer crackers
6 . British English old-fashioned informal a very attractive woman