a cake boy is someone light and fluffy, effeminate, not where its at, not meaty in the slightest sense of the word.
the opposite of a cakeboy being a 'meat boy'(see 'meat boy').
-" Well surely you must be mistaken, Lawrence is as meaty as they come."
-'' No, no he's not. Look in his eyes and tell me he's there, tell me he's not a cake boy.''