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

Vivian: "Girl, didn't he take a picture of her naked and use it to blackmail her for more sex?"
Rebecca: "Yeah, first the blackmail, then the black rail!"
Rebecca: "Yeah, first the blackmail, then the black rail!"
by Im A Beast September 5, 2021

by RestoredByzantineEmpire June 13, 2020

A person who is defined as rail-worthy is someone you wouldn't usually rail (fuck), however, you have become ever so enchanted by there personality and wit, that they are now worthy of a good railing (fucking).
’I wasn't too sure about Jenifer ... But after a long conversation I had with her last night.. I find that she is now rail-worthy’ said Sam
by AstrayMind98 April 12, 2020

by aesop November 6, 2003

dude1: "Bro, did you see that fly honey over there?"
dude2: "Yeah dude, I'm getting ready to rail that gash. get pumped."
dude1: "Deal."
dude2: "Yeah dude, I'm getting ready to rail that gash. get pumped."
dude1: "Deal."
by sebastian crucial, d loke, gsb January 18, 2007

When she is lined upon reverse cowgirl and about to come down but you miss both holes and hit the taint
by PinHeadLarry3 November 9, 2017
