||Ab`a*cis"cus (b`*ss"ks), n. [Gr. 'abaki`skos, dim of 'a`bax. See Abacus.] (Arch.) One of the tiles or squares of a tessellated pavement; an abaculus.
Ab"a*cist (b"*sst), n. [LL abacista, fr. abacus.] One who uses an abacus in casting accounts; a calculator.
A*back" (*bk"), adv. [Pref. a- + back; AS. on bæc at, on, or toward the back. See Back.] 1. Toward the back or rear; backward. "Therewith aback she started." Chaucer.