- One upmanship is defined as the practice of always trying to be better than or gain superiority over others.
An example of one-upmanship is when you wait to announce your wife is pregnant until the dinner at which your brother announce he is engaged, just to take the attention off of your brother.
one-upmanship definition by Webster's New World
Origin: one-up plush (games)manship
one-upmanship definition by American Heritage Dictionary
also one-ups·man·shipnoun Informal