When you get someone to smile really wide to expose their braces, then rub the head of your dick all over their braces from side to side while blowing on a wooden train whistle.
Guy 1: So what did you get up to last night?
Guy 2: Man, this bitch at the bar wanted me to give her the TennesseeTraintracks so I took her home and blew my wood whistle all over her nasty whore mouth.
The region of hair in between your balls and asshole. To develop a tainthawk all other hair on testicles and testicle area as well as most of exposed asshole hair which varies from person to person must be removed. Resulting in an upside down mo-hawk in the taint area only. Hence tainthawk
n. when you have braces on the top and bottom row of your teeth, giving the wearer the look of having mini traintracks running through their mouth.
the gaps between your teeth are the bars and your braces are the tracks.
rebecca: guess who's getting traintracks?
courtney: who?
rebecca: simon! he's also going to the sameorthodontist as me!
courtney: doesn't mei go to that one too?
rebecca: oh, whoops...
What the train rides on... a slang term for a woman who gets a train pulled on her, or has sex with one guy after another after another and so on and so forth.