Pale pigmentation and pasty skin caused by excessive exposure to Cathode Ray Tube (CRT) Screens. This 'tan' generally applies to Caucasians only, but some Hispanics and Middle-Eastern people have been known to see the same effect.
The acronym CRT can also be used to express 'Cathode Ray Tan'
"Hey Archibald, me and the boys are going to spy on the girls in their change rooms, are you coming?"
"Sorry Fred, I'm busy working on my cathode ray tan. Maybe later."