[agent-n. f. KNUCKLE v.]
1. Thieves slang. A pick-pocket.
1834. H. Ainsworth, Rookwood, III. v. No knuckler so deftly could fake a cly.
2. A schoolboys marble used in knuckling.
1896. Crockett, Cleg Kelly, ii. 7. One noble knuckler of alabaster.