1. the U.S. department consisting of practically all military aviation forces, established July 26, 1947.
2. (l.c.) a similar department in any military organization.
3. (l.c.) (formerly) the largest unit in the U.S. Army Air Forces.
4. (l.c.) a unit of U.S. Air Force command between an air division and an air command.
5. (sometimes l.c.) the military unit of a nation charged with carrying out military operations in the air.
6. Brit.Royal Air Force.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.