letters and packages that are transported by aircraft
"The collector spent hours sorting through his vintage airmail stamps, each one representing a letter or package once transported by aircraft across the ocean."
The system of conveying mail using aircraft.
"The package was sent via airmail to ensure it reached its destination quickly."
In plain English: Airmail is mail that gets sent by airplane instead of trucks or trains to reach its destination faster.
"We decided to send our wedding invitations by airmail so they would arrive in time for the big day."
Usage: Use this term to refer specifically to postal services delivered by plane, rather than the general concept of sending letters quickly. It is often confused with "surface mail," which implies delivery via ground transport only.
To send mail by air.
"I decided to send my urgent letter via airmail so it would arrive quickly."
The word airmail is formed by combining the words air and mail to describe letters or packages sent by airplane. It entered English as a straightforward compound term reflecting this new method of delivery.