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8.
This is when you kiss a women after licking her out, while she's on her period. The period blood should collect in your mouth and during the kiss you pass it onto her.

NOTE: If you wanna try this be aware that you can actually catch HIV from doing this as you're swaping blood.
"My boyfriend gave me a rainbow kiss"
by Blooddiamond21 August 31, 2007
 
9.
The act of a guy jizzing in a girls mouth and a girl getting period blood in a guys mouth, then kissing and sloshing it all together
Luke and I rainbow kissed last night... Never doing that again!
by Kingshockey66 April 07, 2014
 
10.
During a girls menstration the male performs oral sex and takes a mouthful of her blood. While the male has blood in his mouth the girl performs oral sex and takes a load. They then exchange a passionate kiss with their body secretions in their mouth through a kiss
When Sean was giving a rainbow kiss, to Vanessa he got a case of the red teeth.
by Killer Joe July 12, 2006
 
11.
when you go down on a girl during her period
girl a 's'pose nothing happened last night cos it's that time of month'

girl b ' actually he gave me a rainbow kiss'

girl a 'never had a guy game enough to do that to me b4'
by lantern January 22, 2007
 
12.
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
 
13.
when a girls on her period and gets licked out then gives him head and they pull straight after.
im on my period finally so now we can have a rainbow kiss.
by doovde January 10, 2008
 
14.
an extention of red socks
once red socks has been achieved the couple kiss and exchange the expelled blood
girl: shall we rainbow kiss now

Guy: (muffled) mmm hmm
by james J.D.R. April 08, 2011