your nailin a girl while she is on her period (with a condom of course) and you shoot into the condom, then you make her drink the contents out of the condom like it is an oddly shaped glass. 'rainbow' comes from the idea of many different colors all draining into her mouth.
my girlfriend was on her period, and she really wanted to fuck, but i wasnt really feelin the whole blood-thing, so i told her i would only if she would 'taste the rainbow.' that bitch slurped it up like the final parts of a milkshake haha.
by vic tha sick dick June 28, 2006
by nomi12791 April 19, 2008
by 'Bow Taster October 29, 2010
by scientific researcher January 17, 2013
by TtlyNotaJew April 11, 2011
Achmed, LeShaun, Jose, Ching-Ming, Eric, and Chief Running-Horse all came into Vanessa's mouth. She really enjoyed tasting the rainbow.
by A Mexican Midget November 09, 2011
by J. Grizz May 04, 2011