Dishevelled, rakish, disorderly, or unkempt. Used of hair, neck ware, or one's general disposition. Opposite of "rectilinear-biff." Origin unknown, but possibly derived from a misunderstanding of "skew-wiff." Usage peculiar to Brasenose College, Oxford.
"My word, Terence, with your tie at that angle, and your obvious bed-head, you're looking unusually skew-biff!"
"Don't worry: I get myself rectilinear in no time."