knuckle up

== English == === Verb === knuckle up (third-person singular simple present knuckles up, present participle knuckling up, simple past and past participle knuckled up) (informal, chiefly African-American Vernacular) To clench one's fist(s) as though in preparation for a fight. (informal, by extension) To approach a problem aggressively. (slang) To strike or fight.