Meaning

• An inexperienced recruit, especially in the police or armed forces.

• A novice.

• An 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.

• A type of firecracker, used by farmers to scare rooks.

Meaning

• Non-professional; amateur

  "The game was going well until I made that rookie mistake."