adaptive optics

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

• noun An imaging system, such as a reflecting telescope, that has optical elements that change shape, adapting to changes in the phenomena being imaged. Such systems allow astronomers to obtain sharp images of celestial objects by adapting to and removing the effects of turbulence in the earth's atmosphere.

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

• noun (Astron.) an optical system used in some telescopes since the 1980's which rapidly changes the shape of the primary reflecting mirror to adjust for distortions of light which are caused by atmospheric turbulence. By reducing the distortions caused by the atmosphere, telescopes fitted with such optics can achieve a higher resolving power than normal telescopes with static mirrors.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun astronomy, optics An optical system in telescopes that reduces atmospheric distortion by dynamically measuring and correcting wavefront aberrations in real time, often by using a deformable mirror.