AAR
- AAR Corporation
- AAR coupling
- AAR wheel arrangement
- Aar
- Aar (Dill)
- Aar (Ill)
- Aar (Lahn)
- Aar (Star Wars)
- Aar (Twiste)
- Aar (village)
- Aare (disambiguation)
- Aarhus Airport
- Adam's apple reduction
- Afar language
- African American Review
- After action report
- After-action review
- Ahr
- Air America Radio
- Air-to-air refueling
- Alkali–aggregate reaction
- All American Racers
- All-American Road
- Allens (law firm)
- American Academy in Rome
- American Academy of Religion
- Amino acid response
- Ann Arbor Railroad (disambiguation)
- Antarctica
- Asiana Airlines
- Association for Automated Reasoning
- Association of American Railroads
- Average accounting return
- Captain Future
- List of SMS abbreviations
- Rifleman
- South American–Antarctic Ridge
- The All-American Rejects