Plain English Meaning
How clearly and sharply you can see detail. Good visual acuity means you can pick out small things clearly; reduced visual acuity means objects look blurry, faint, or harder to make out.
Full Definition
The sharpness of vision — the eye's ability to resolve fine detail and distinguish small objects clearly at a given distance. Visual acuity depends on the health of the eye, lighting conditions, and the part of the retina being used to view the object.
Context Anchor
Used in night vision training when discussing how well a pilot can see detail in daylight, darkness, and low-light cockpit conditions.
Derivation
From the Latin 'acuitas', meaning sharpness or keenness, from 'acus' (needle). Combined with 'visual', it literally means 'sharpness of sight' — a useful reminder that acuity is about precision of vision, not just whether you can see.