to fight a single match

nuclear reaction

warfare involving physical combat instead of weapons / (figuratively) activity involving large amounts of physical contact, especially sports

regular game, regular season

psychological warfare

a contest (for a trophy, a title, etc...)

(Japanese phonology) an accent kernel/nucleus (the so-called "accented" mora of an utterance, which singly occurs for each utterance and which immediately precedes a drop in pitch from high to low)

(historical) battleaxe, poleaxe

battle of the brains

(sports) a game/match between teams from Waseda University and Keio University