A fair question! The term gets bandied about this website quite regularly. Dictionary.com provides a few definitions and this is the one closest to how I tend to use it.
one-up.man.ship n.
Informal
The art of outdoing or showing up a rival or competitor, as in exploits, privileges, or honors.
Etymology: 1952, from noun phrase one up "scoring one more point than one's opponent" (1919).
http://dictionary.reference.com/browse/one-upsmanship
3/12/2008
