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1. When a continuous signal sampled at discrete points cannot be reconstructed unambiguously due to insufficient information; artifacts introduced by insufficient sampling, for example when diagonal lines and curves in a digital image become distorted due to low resolution

1. (technical) have a signal at frequency appear as a different frequency due to inadequate sampling
    
2. (computing) give an additional equivalent name to an entity, for example one that's more user-friendly

Encyclopedia: Aliasing