Plain English Meaning
A check by the FAA to confirm that an aircraft or part has been built precisely the way the approved plans say it should be built.
Full Definition
A formal inspection conducted by the FAA (or its designee) to verify that a prototype aircraft, component, or part has been built exactly in accordance with its approved type design data — the engineering drawings, specifications, and materials specified during certification.
Context Anchor
Seen in aircraft certification and airworthiness discussions, especially when an aircraft, part, or major change must be shown to match approved design data.
Derivation
From Latin 'conformare' — to shape together, to match. A conformity inspection literally checks whether the finished article matches the shape it was supposed to be made to.
Why Pilots Care
It is one of the gates before a new or modified aircraft receives its and can legally fly.