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: Webster's Revised Unabridged Dictionary (1913)