magnum opus

something (as a work of art) that is a great achievement and often its creator's greatest achievement this symphony is usually considered Beethoven's magnum opus Synonyms chef d'oeuvre, classic, masterpiece, masterworkRelated Words masterstroke, pièce de résistance, showpiece, tour de force; blockbuster, megahit, smash, success, winner; gem, jewel, prize, treasureNear Antonyms bomb, catastrophe, clunker, debacle (also débâcle), disaster, dud, failure, fiasco, fizzle, flop, loser, turkey, washout