first-class

(noun) the highest rank in a classification. Synonyms: first class.

(noun) mail that includes letters and postcards and packages sealed against inspection. Synonyms: first class, 1st class, first-class mail, 1st-class mail.

(noun) the most expensive accommodations on a ship or train or plane. Synonyms: first class.

(adj) very good;of the highest quality. Synonyms: excellent, fantabulous, splendid. Examples: "Made an excellent speech." "The school has excellent teachers." "A first-class mind."

(adv) by first class conveyance; with first class accommodations. Synonyms: first class. Example: "We always travel first class."