Show-er
A man whose penis is large in its flaccid state, but only grows marginally when he is fully erect. An example of this would be a man who is 6in flaccid, and 9in erect. The opposite of this would be a grower.
Guy #1: Hey man, did you see that guy's dick? It's like 7 inches... SOFT!!

Guy #2: Yeah, that's crazy. He's probably a show-er, though. I bet you he's no bigger than 8.5 inches erect.