1 A deviation from what is normal, usual, or right. See also chromosomal aberration.
2 A temporary lapse of behaviour or mental function.
3 A defect of the crystalline lens of the eye, or of any other lens or mirror, also called astigmatism or dioptric aberration, in which rays of light do not all converge on to a single focal point. In chromatic aberration, different wavelengths of light are refracted through different angles and focused at different distances, leading to blurred images with coloured fringes—see also achromatic (2), refraction. In spherical aberration light passing through the lens near its edge is focused at a different point from light passing near the lens's centre, resulting in a distorted visual image, the defect arising from the surface of the lens being spherical. [From Latin aberrare to wander away, from ab away + errare to wander + -ation indicating a process or condition]