Definition of score off:
(v) :
(transitive, inseparable, idiomatic, slang) To defeat (especially in an argument), get the better of, achieve a success over, gain an advantage or win points over, make a point to the detriment or at the expense of, make appear foolish. Sometimes with particle on (someone).
(v) :
(transitive, separable, idiomatic) To delete or remove (especially from a list); to score out, strike out or strike off, cross out or cross off; to draw a line through.
(v) :
(archaic, slang, transitive) To defeat (someone) verbally; to win a confrontation with words; to tell (someone) off.
(v) :
Used other than figuratively or idiomatically: see score, off. To score from.