noun
rookie athlete; rookie fighter
Wasei-eigo term used especially in boxing and combat sports for a young, inexperienced competitor. Not used for general beginners.
wasei-eigo (Japanese-coined English), from green boy
彼はまだグリーンボーイだが、将来が楽しみだ。
He's still a green boy, but his future looks promising.
Matches between green boys are rough but interesting.