Undesirable ‘beating’ effects caused by sampling frequencies being too low faithfully to reproduce image detail. Examples are:

1) Temporal aliasing – e.g. wagon wheel spokes apparently reversing, also movement judder seen in the output of standards converters with insufficient temporal filtering.

2) Raster scan aliasing – twinkling effects on sharp boundaries such as horizontal lines. Due to insufficient filtering this vertical aliasing and its horizontal equivalent
are often seen in lower quality DVEs as detailed images are compressed.

The ‘steppiness’ of unfiltered lines presented at an angle to the TV raster is also referred to as aliasing.

See also: Anti-aliasing, Interpolation (temporal & spatial)