1. (n) An individual who, in any given conversation, will not hesitate to barge in with an anecdote of often questionable eligibility that in some way makes him better than anything you've said so far in the conversation
2. (v) To commit the act described in being a One-up James
Becky: So I adopted a kitten from the SPCA the other day, he's SO cute!
One-up James: Funny you should mention that, Becky, I just adopted Five kittens that I saved from a burning skyscraper last weekend
Becky: But aren't you allergic to cats?
OUJ: Oh, I was, then I developed the cure for anything