A Phrase used in calling someone's bluff or in casually suggesting that they are flat out lying to you or others. Can be used as a sarcastic command to deter a person from lying, or as a verb, generally in past or future tenses.
Command: "There's no way you survived a car crash like that. Story up, man, story up."
Verb: "I'll have to story up if she asks me where I've been."
Seat 7: Come on, if you straddle this bet, I'll blind raise $15.
Seat 6: I don't straddle, besides, $15 is too small.
Seat 7: Well what do you want?
Seat 6: Stone up and bet $50