aberration

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A deviation from what is considered proper or normal. synonym: deviation.
• noun A departure from what is typical.
• noun Psychology A disorder or abnormal alteration in one's mental state.
• noun A defect of focus, such as blurring in an image.
• noun An imperfect image caused by a physical defect in an optical element, as in a lens.
• noun The apparent displacement of the position of a celestial body in the direction of motion of an observer on Earth, caused by the motion of Earth and the finite velocity of light.
• noun Genetics A deviation in the normal structure or number of chromosomes in an organism.

from The Century Dictionary.

• noun The act of wandering away; deviation; especially, in a figurative sense, the act of wandering from the right way or course; hence, deviation from truth or moral rectitude.
• noun In pathology: A wandering of the intellect; mental derangement.
• noun Vicarious hemorrhage.
• noun Diapedesis of blood-corpuscles.
• noun Congenital malformation.
• noun In zoology and botany, deviation from the type; abnormal structure or development.
• noun In optics, a deviation in the rays of light when unequally refracted by a lens or reflected by a mirror, so that they do not converge and meet in a point or focus, but separate, forming an indistinct image of the object, or an indistinct image with prismatically colored edges.
• noun In astronomy, the apparent displacement of a heavenly body due to the joint effect of the motion of the rays of light proceeding from it and the motion of the earth.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of wandering; deviation, especially from truth or moral rectitude, from the natural state, or from a type.
• noun A partial alienation of reason.
• noun (Astron.) A small periodical change of position in the stars and other heavenly bodies, due to the combined effect of the motion of light and the motion of the observer; called annual aberration, when the observer's motion is that of the earth in its orbit, and daily or diurnal aberration, when of the earth on its axis; amounting when greatest, in the former case, to 20.4'', and in the latter, to 0.3''. Planetary aberration is that due to the motion of light and the motion of the planet relative to the earth.
• noun (Opt.) The convergence to different foci, by a lens or mirror, of rays of light emanating from one and the same point, or the deviation of such rays from a single focus; called spherical aberration, when due to the spherical form of the lens or mirror, such form giving different foci for central and marginal rays; and chromatic aberration, when due to different refrangibilities of the colored rays of the spectrum, those of each color having a distinct focus.
• noun (Physiol.) The passage of blood or other fluid into parts not appropriate for it.
• noun (Law) The producing of an unintended effect by the glancing of an instrument, as when a shot intended for A glances and strikes B.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a disorder in one's mental state
• noun a state or condition markedly different from the norm
• noun an optical phenomenon resulting from the failure of a lens or mirror to produce a good image