\A*back"\ ([.a]*b[a^]k"), adv. [Pref. a- + back; AS. on
b[ae]c at, on, or toward the back. See {Back}.]
1. Toward the back or rear; backward. ``Therewith aback she
   started.'' --Chaucer.
2. Behind; in the rear. --Knolles.
3. (Naut.) Backward against the mast; -- said of the sails
   when pressed by the wind. --Totten.
{To be taken aback}.
   (a) To be driven backward against the mast; -- said of the
       sails, also of the ship when the sails are thus
       driven.
   (b) To be suddenly checked, baffled, or discomfited.
       --Dickens.

\Ab"ack\ ([a^]b"ak), n.
An abacus. [Obs.] --B. Jonson.