Definitions
1.nounAn inexperienced recruit, especially in the police or armed forces.
2.nounA novice.
3.nounAn athlete either new to the sport or to a team or in his first year of professional competition, especially said of baseball, basketball, hockey and American football players.
4.nounA type of firecracker, used by farmers to scare rooks.
5.adjectiveNon-professional; amateur"The game was going well until I made that rookie mistake."