n. A front or boundary, especially one between military, political, or ideological positions.n. Basketball See frontcourt.n. Football The linemen of a team.n. Sports The players who play farthest forward, as in volleyball.adj. Located or used at a military front.adj. Of or relating to the most advanced or important position or activity in a field or undertaking: "leaders of the six black 'front-line states' bordering South Africa” ( Boston Globe). adj. Sports Of or relating to the frontline.adj. Sports Being a member of the regular team; first-string: a team in need of a frontline catcher.