U.S.A.F.

or USAF

United States Air Force

noun
  1. the permanent or regular military air force of the United States, established in 1947 as a separate service under the authority of the Department of Defense: a branch of the U.S. Army before 1947. Abbreviation: USAF
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for usaf

USAF

abbreviation for
  1. United States Air Force
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012