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1 definition by Perkynips2001

Rainblow is when you are performing oral sex on a man, and its really big, your mouth starts to water down the shaft as your gag reflex kicks in, ,and then use it for lube, as you are jerking him off and sucking his cock
"The guys cock was so big lastnight, I had to rainblow him"
by Perkynips2001 July 07, 2005