Rainblow is the practice of having several females, each wearing differant colored lipstick, performing oral sex on a man. This will leave a rainbow effect on his penis.
The girls at the party last night gave me a colorful rainblow.
When a girl performs Oral Sex on you while she is eating Skittles.
Guy: Dude that chick gave me a Rain Blow in the bathroom!
Guy2: No Wai!
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"
A practice, common among hetersexual men, of recieving felatio from homosexual men. This stems from the belief that homosexual men give better head.
It is important to note that participating does not compromise one's sexuality.
Kris, feeling stressed out, decided to get rainblowed by his neighbor.
When a man gives oral sex to another man.
Last night I gave my pal Tom a rainblow!