WordNet sense 1 (the cardinal number that is the sum of one and one and one):

leash, three, trey, triad, trinity, trio, triplet, troika, deuce-ace, III, tercet, ternion, terzetto, tierce, trine

WordNet sense 2 (having three units or components or elements):

treble, triple, triplex

WordNet sense 3 (having or involving or consisting of more than one part or entity or individual):

multiple