n.1.a class mail comprising letters, postcards, and other mail sealed against inspection, having a higher priority than second, third, or fourth-class mail; - it is the highest class of mail not handled in a special manner, as is registered or priority mail.
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
1st-Class Releases Product with Hypertext and Expert System Technology
A hypertext editor in 1st-CLASS HT allows developers to organize information into "cards." They can then establish structural links by selecting the information on one card that can be used to point to information on another.
1st-CLASS HT also lets developers use hypertext to build custom screens and windows.