Definition from Wiktionary, the free dictionary
Short for shove it up your ass.
- (idiomatic, offensive, markedly vulgar) Expression to show discontent with the other party, or to show contempt.
- You dare come here dressed so horribly? Well, up yours!
- (idiomatic, dismissive, offensive, markedly vulgar) Go away! Go to hell!
- Up yours!—I’m not giving you any!
- You’ve done enough to ruin our outing, so up yours!
exclamation of contempt — see shove it up your ass