aberration

noun

• a departure from what is normal, usual, or expected, typically an unwelcome one:they described the outbreak of violence in the area as an aberration I see these activities as some kind of mental aberration
• Biology a characteristic that deviates from the normal type:colour aberrations
• Optics the failure of rays to converge at one focus because of a defect in a lens or mirror.
• Astronomy the apparent displacement of a celestial object from its true position, caused by the relative motion of the observer and the object.