Viewing something, usually nature-related, so intensely beautiful that you can't even capture on your camera.
Liz: Oh my god, Emerald Bay is so GREEN. ITS SO GREEN.
You: I know you're having a Double Rainbow moment but you need to calm down or you'll fall off the edge.
When a guy is eating out a girl the shoves a pack of skittles up her vagina without her consent. He then performs the ABC's making her cum a rainbow, which he thinks makes her cum sweeter.
Last night Tom was eating out this chick, he shoved a pack of skittles up her cooch and performed the ABC's on her, she came a rainbow. example Cuming Rainbow
The act of throwing Skittles at another person and saying "Feel the rainbow!"
*Person 1 throws Skittles at Person 2*
Person 2: What did you do that for?
Person 1: Feel the rainbow!
Person 2: Isn't it 'Taste the rainbow'?
Person 1: Well, the Skittles aren't in your mouth!
When you go shit in his mouth, he goes shit in yours, and you French kiss.
Also, when a guy goes down on a girl while she is on her period, and Gets all the blood in his mouth. And a girl has blood/cum in their mouth, they kiss each other.