Aliasing
The misrepresentation of detail finer than a sampling system can resolve, appearing as false structure rather than as blur.
In depth
Aliasing is a general property of sampling, familiar from wagon wheels appearing to turn backwards in film. In stills it manifests as moiré, false colour and jagged diagonal edges. The only true remedies are to sample more finely — more pixels — or to filter out the offending detail before it reaches the sensor.
Examples in practice
A tiled roof photographed from a distance shows a stepped, shimmering pattern rather than clean rows.