In the enlish lands of enlang a person going down on a women on her period is right also in some of the US.

But, the most recent i found out is when a guy gets a few chicks together. Each wearing a different color lip stick. Each girl trys to get the lip stick the furthest down on the guys hard penis.
John decided to get his girl and friends to rainbow kiss him.
by ShadowJester January 22, 2005
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When you have sex, when the gurl iz on her period. Both partners suck the gurls blood and the boys cum into their mouths, and then they french kiss then swallow the remenants.
Katy : Me and Jim performed a rainbow kiss last night!
Jill : Did the cum taste nasty?
by Lupe Fiasco April 22, 2006
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When a guy eats out a girl with her period then she blows him then they kiss with all of the stuff in their mouth
by Lexi November 25, 2003
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When a girl os on her period and the guy sucks her pussy and the girl sucks his cum and they exchange in a kiss....
U gave Sheran a rainbow kiss last night...heavy and colorful ...
by Danienellie August 11, 2006
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When a female is recieving oral sex on her menstral cycle and the person performing kisses her afterward.
Betty gave sarah rainbow kisses
by Liz November 20, 2002
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when a guy puts period juce from a menstruating girl and makes out with her wtih th juice still in his mouth
Tim likes to rainbow kiss with his bitch
by homerice69 March 2, 2005
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When a girl is on her period and a guy licks her out.
Can also be when a guy licks out a girl when on her period and he kisses her after licking the pussy and transfers the period blood back into her mouth.
Only a real whore would attempt this.
1. I just gave this girl a rainbow kiss
2. You are fucking disgusting!

1. Never try a rainbow kiss, you will throw up
2. I know, me and this whore did it last night and we threw up in eachothers mouth !
by what was that! August 27, 2010
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