Other forms: faced off; facing off; faces off
When you face off against someone, you compete with or oppose them. There's nothing better than watching your favorite team face off against their biggest rival.
This phrase comes up often in sports, like when a young tennis prodigy faces off against a champion or two football teams face off in the Super Bowl. Face off is an official term in ice hockey, meaning "start or restart play, with two players facing each other." You can use it for any combative opposition, from war to a bitter argument with your sister: "Once again, we face off over whose turn it is to wash the dishes."