leader of a group of juvenile delinquents; gang leader
Refers to the boss of a school-based or neighborhood youth gang, often in a delinquent subculture context. The term carries a rough, old-school image and is common in manga and anime.
He was famous as the gang leader of this school.
He was feared as the gang leader when he was in junior high school.
The protagonist of that manga becomes the boss of the delinquents at his new school.
He won a fight and became the gang leader.
He always acts like he's the gang leader.
ガキ大将 is the childish leader of a group of kids, a milder and less delinquent image than the tougher, older-style 番長.
班長 sounds similar to 番長 but means the leader of a small work or class group, with no delinquent connotation at all.
fashion leader; fashionista
Compound of 番 (ban, 'watch' or 'number') and 長 (chō, 'leader'). The exact historical derivation is uncertain, but the term likely originated in school slang for the head of a group of troublemakers.