Used when a person puts down (disses) someone or a group of people subtly (in "disguise") with hidden meaning, either intentionally, or unbeknownst to themselves.
"Hey, why don't you come to my awesome party? I've invited all of our friends."
"That's nice. Have you invited other people aside from our circle of friends? Like say, any hot chicks?"
"Woah that's a dissguise if I ever saw one!"