Green’s Dictionary of Slang

rucker n.

[ruck n.2 (1)]

1. an arguer, a combative person.

[UK]Partridge DSUE (8th edn) 995.1: since ca. 1955.

2. a fighter.

[UK]Partridge DSUE (8th edn) 995/1: 1970s.
[UK]K. Sampson Awaydays 5: There’s some good little ruckers there.