Fat"ly, adv. Grossly; greasily. Fat"ner (?), n. One who fattens. [R.] See Fattener. Arbuthnit. Fat"ness, n. 1. The quality or state of being fat, plump, or full-fed; corpulency; fullness of flesh. Their eyes stand out with fatness. Ps. lxxiii. 7.