An anus that looks big enough to navigate a train through. An anus that resembles a tunnel going into a mountain.
I was going to fuck the bitch but as I tried I accidentally fell in her trainus and had to be extracted by the jaws of life.
by Phil M June 16, 2004
An anus that has been trained to fart as soon as a wife and or girlfriend has left the room.
A fart snuck out of Tyler's trainus as soon as Bailey left the room.
by Jiggles6 February 01, 2011