Used to descirbe something/someone epicly amazing... Like me! Do not use this on someone/something who is obviously not a triplekickassrainbow. Usually used to describe cookie monster cupcakes.
Pix: Kyra kyr, your a triplekickassrainbow!
Me: awww thanks Pix :D
or
This cupcake taste like a triplekickassrainbow!
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.