Source : Webster's Revised Unabridged Dictionary (1913)

First-class \First"-class`\, a.
   Of the best class; of the highest rank; in the first
   division; of the best quality; first-rate; as, a first-class
   telescope.

   {First-class car} or {First-class railway carriage}, any
      passenger car of the highest regular class, and intended
      for passengers who pay the highest regular rate; --
      distinguished from a second-class car.

Source : WordNet®

first-class
     adj : of the highest quality; "made an excellent speech"; "the
           school has excellent teachers"; "a first-class mind"
           [syn: {excellent}, {fantabulous}]

first-class
     adv : by first-class conveyance; with first-class accommodations;
           "we always travel first class"