look up any word, like jamflex:
 
1.
1: A colorful, challenging course finalizing the Special Cup in the Nintendo Mario Kart game series.
2: An annoyance.
3: The bane of one's existence.
"SHIT FUCK, GODDAMN YOU RAINBOW ROAD!"
(Often used during game play, after falling off course 4 times in a row.)

or

"I can't believe that stupid asshole picked Rainbow Road again."
(Often used during WFC Wii Online play)
by HollyMarieP May 16, 2008
 
2.
When you have a bowl movement and a flurry of fruity pebbles lands on the ground beneath you.
Kid 1: "I had a rainbow road in the middle of class when my teacher wouldn't let me go to the bathroom."

Kid 2: "Damn dude that sucks."
by GEArSofWAr873 July 24, 2010
 
3.
When 2 or more girls (preferably more), each with a different color of lipstick, compete to see who can get their lipstick the lowest down on your dick
"Dude! The other day Sarah and her friends gave me a Rainbow Road, Jessica came first with purple"
by kcbxo April 16, 2014
 
4.
rainbow road is the term used for a line of ecstacy that is from pills of various colours.
did ricky actually just snort that rainbow road?!?!
yeah dude hes not coming back anytime soon.
by n!ckA$$ April 10, 2009
 
5.
When a male ejaculats all over a female; see 'rainbow'
"last week my girlfrined asked me if I could rainbow road her"
by sean & nina July 11, 2005