Synonym for wanker. Probably in reference to the colour of male masturbatory production. Only ever heard the term used by people from or connected to Aberdeen, Scotland.
Usually prefaced with the word "hemmin" a contraction of "hey man" - e.g. "Hemmin ya whiter"
Term of abuse. Possible reference to the colour of sperm. Can be used in the same way that you would use the term "wanker": as a general term of abuse rather than a direct accusation of self-abuse. Used in and around Aberdeen, NE Scotland.
"ken 'at boy over there, he's a fuckin' whiter"