/tri tag"euh nist/ , n.
(in ancient Greece) the third member of an acting troupe, which always consisted of three actors. Cf. protagonist (def. 4), deuteragonist .
[ 1885-90; tritagonistés, equiv. to trit ( ós ) THIRD + agonistés actor, competitor, agent deriv. of agonízesthai to contend, struggle, compete for the acting prize ]