Pronunciation: (kwin-tes'uns), [key]
1. the pure and concentrated essence of a substance.
2. the most perfect embodiment of something.
3. (in ancient and medieval philosophy) the fifth essence or element, ether, supposed to be the constituent matter of the heavenly bodies, the others being air, fire, earth, and water.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.