duelist

Concise Oxford English Dictionary © 2008 Oxford University Press:
duel/ˈdjuːəl/

▶noun chiefly historical a prearranged contest with deadly weapons between two people to settle a point of honour.

■ (in modern use) a contest between two parties.

▶verb (duels, duelling, duelled; US duels, dueling, dueled) fight a duel.

– derivatives
dueller (US dueler) noun,
duellist (US duelist) noun.

– origin C15: from L. duellum, archaic and literary form of bellum ‘war’, used in med. L. with the meaning ‘combat between two persons’, influenced by dualis ‘of two’.