Plain English Meaning
It is the official FAA rulebook for what you need to know and be able to do to earn a pilot certificate or rating. Your instructor trains you to it, and the examiner tests you against it.
Full Definition
The FAA document that defines what an applicant must know, consider, and be able to do to pass a specific pilot certificate or rating. The ACS combines aeronautical knowledge, risk management, and flight proficiency into a single integrated standard that examiners use to test applicants and that instructors use to train them.
Context Anchor
You will see the ACS when preparing for a pilot test, planning training with an instructor, or checking what an examiner is expected to evaluate.
Derivation
Airman is the long-standing FAA term for any certificated aviator. Certification refers to the formal of being to act as a pilot. means the fixed benchmarks used to judge whether the applicant meets the requirement. Together: the standards used to certify an airman.