The Collaborative International Dictionary
To knuckle to
Knuckle \Knuc"kle\, v. i. [imp. & p. p. Knuckled;; p. pr. & vb. n. Knuckling.] To yield; to submit; -- used with down, to, or under. To knuckle to.
To submit to in a contest; to yield to. [Colloq.] See To knock under, under Knock, v. i.
To apply one's self vigorously or earnestly to; as, to knuckle to work. [Colloq.]