knock someone's block off
knock (one's) block off
To strike someone with great force, usually in the head. If you insult me like that again, I'll knock your block off!
knock someone's block off
Beat up someone, as in If he doesn't leave at once, I'll knock his block off. This hyperbolic term employs block in the sense of "head," a usage dating from the 1600s. The idiom, however, dates only from about 1900. Also see beat the living daylights out of.
knock someone's block off
hit someone very hard in anger. informalBlock is used here in its informal sense of ‘head’.