\Crack"a*jack`\, n.
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.]

\Crack"a*jack`\, a.
Of marked ability or excellence. [Slang]