A number that is used to describe really enormous quantities. It has no definitive number of digits, and is not one technical number; instead it is the collectiveness of all numbers that are bigger than the real number that has been brought up just before it. It is often used in much the same way infinity is, when attempting to name a larger amount than one's opponent.
The number derives from the extremely popular podcast, Keith and the Girl (katg.com), during which Keith (one of the two main co-hosts) is known to use the word frequently. It has, from this, spread into common teenage slang.
A: "I'm a million times cooler than you."
B: "No, I'm a trillion times cooler than you."
A: "No, I'm a google times cooler than you."
B: "No, I'm a bubillion times cooler than you!"
A: "Shit - can't top that."