person without a dan rank
Used in martial arts, go, shogi, and similar ranking systems for someone who has not yet attained a dan (black-belt equivalent) rank. Often contrasted with 有段者.
See also: 有段者
He is still a non-dan holder, but he is very strong.
This tournament is open to non-dan holders as well.
Compound of 無 (mu, 'without') + 段 (dan, 'dan rank') + 者 (sha, 'person').