A large, undefined number. Could refer to several, or a massive amount. Used in extreme over-exaggeration for humorous or emphatic purposes
Me: there's like a gajillion stars, we're so infintesimal.
Friend: dude, infintesimal isn't a word
Me: yuh huh. *nods*
Friend: STFU and pass the pipe PLZTHX
The amount of money (in dollars) that Zack owes Nilan, because Zack bet that the radius of convergence was 1/2, when it was really 2. Zack then tried to bet on a coin flip to win his gajillion back, but instead just lost another gajillion.
I now have two gajillion dollars, courtesy of Zack.