In signal processing and related disciplines, aliasing refers to an effect that causes different signals to become indistinguishable (or aliases of one another) when sampled. It also refers to the distortion or artifact that results when the signal reconstructed from samples is different from the original continuous signal.
Aliasing can occur in signals sampled in time, for instance digital audio and is referred to as temporal aliasing. Aliasing can also occur in spatially sampled signals, for instance digital images. Aliasing in spatially sampled signals is called spatial aliasing.
Read more about Aliasing: Description, Bandlimited Functions, Bandpass Signals, Sampling Sinusoidal Functions, Historical Usage, Angular Aliasing