A portmanteau of the slang term "dih" and "silhouette."
It refers specifically to the phenomenon where a man exits a body of water - be it a pool, ocean, or lake - and his wet swimwear suctions to his skin, revealing a clear, unmistakable outline of his genitalia for the public to see.
I saw that video of the actorcoming out of the Mediterranean and the dihouette was crazy.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi