adjective

judged over a period of time to be of the highest quality and outstanding of its kind.

a classic novel

definitive,authoritative,outstanding,of the highest quality,first-rate,first-class,best,finest,excellent,superior,masterly,exemplary,consummate,ideal

noun

a work of art of recognized and established value.

his books have become classics

definitive example,model,epitome,paradigm,exemplar,prototype,outstanding example,paragon,great work,masterpiece,masterwork,established work,standard,pièce de résistance