amateur sumo
Refers to sumo wrestling practiced at an amateur level, as opposed to professional (大相撲). Used in contexts like university clubs, local tournaments, and international competitions.
He does amateur sumo at university.
The national amateur sumo tournament will be held next month.
Compound of アマ (ama, 'amateur') and 相撲 (sumō, 'sumo'). The katakana prefix アマ is a common abbreviation for 'amateur' in Japanese.