"English" is applied to a cue ball by hitting said ball off center. Once the ball has been struck, "body English" is a sort of "dance move" by which the player seeks to further influence the ball's motion.
If we knew the context was about a ball game of some sort, then the literal (i.e. original) meaning, as cyber has posted, would be the intended meaning. The term has also been used to describe "body language" more generally, i.e., outside the context of ball games.