A combination of an Uke and a Seme. A Seme being the more dominant, experienced, or 'top' partner, while an Uke being the more docile, inexperienced, submissive and 'bottom'.
A Suke is someone who on the outside, would look or act like a Seme. Would be a more dominant personality, and think that they are a 'total Seme' but in bed, will basically submit and be the Uke.
Or a person who trys to be Seme in bed but ends up being submissive.
Usually used in Yaoi.
Dave "Ohh hes such a Suke. He thinks hes a big tough guy. Guess not!"