“A.F.” is an abbreviation that can mean different things depending on context:

• Air Force
  • Example: U.S. A.F. = United States Air Force
• As F* (informal slang, censored form)**
  • Used for emphasis (e.g., tired A.F. = very tired)
• Ante meridiem form / date shorthand (rare)
  • Sometimes used in older or technical notation, but uncommon today

In short, A.F. most commonly means “Air Force” in official contexts, or “as f*” in informal slang.**