Someone who appears to be thin with clothes on, but their body is actually flabby, mushy, or cellulite-ridden.
Girl 1: "I wish I had Natalie's body."
Girl 2: "No you don't. I've seen her in a bathing suit, and she's a total mush-rail."
Girl 2: "No you don't. I've seen her in a bathing suit, and she's a total mush-rail."
by Julie F. and Julie B. April 22, 2008
Get the mush-railmug.