A) An image artefact that occurs when a pattern is created on the screen where there should not be one. The moiré pattern is generated when different frequencies that are part of the video signal, create a new unwanted frequency. b) A wavy pattern, usually caused by interference.

When that interference is cross-color, the pattern is colored, even if the picture is not. c) The spurious pattern in the reproduced television picture resulting from interference beats between two sets of periodic structures in the image. It usually appears as a curving of the lines in the horizontal wedges of the test pattern and is most pronounced near the centre where the lines forming the wedges converge. A Moiré pattern is a natural optical effect when converging lines in the picture are nearly parallel to the scanning lines.