• (a.) Of marked ability or excellence. • (n.) A preparation of popped corn, candied and pressed into small cakes. • (n.) An individual of marked ability or excellence, esp. in some sport; as, he is a crackajack at tennis. Found on http://thinkexist.com/dictionary/meaning/crackajack/
Crack'a·jack` noun 1. An individual of marked ability or excellence, esp. in some sport; as, he is a crackajack at tennis. [ Slang] 2. A preparation of popped corn, candied and pressed into small cakes. [ U. S.] Found on http://www.encyclo.co.uk/webster/C/179