the fact or an instance of deviating or being aberrant especially from a moral standard or normal state. something or someone regarded as atypical and therefore able to be ignored or discounted. failure of a mirror, refracting surface, or lens to produce exact point-to-point correspondence between an object and its image. unsoundness or disorder of the mind. a small periodic change of apparent position in celestial bodies due to the combined effect of the motion of light and the motion of the observer. an aberrant individual.