n. 1 the most essential part of any substance; a refined extract. 2 (usu. foll. by of) the purest and most perfect, or most typical, form, manifestation, or embodiment of some quality or class. 3 (in Ancient Philosophy) a fifth substance (beside the four elements) forming heavenly bodies and pervading all things. quintessential adj. quintessentially adv.
[ ME (in sense 3) f. F f. med.L quinta essentia fifth ESSENCE ]