D defs.my
Entry 4 senses · 2 variants Webster, 1913

Aback

/(ȧ*băk")/ · A·back · IPA /əˈbæk/
01 adv. Toward the back or rear; backward.
  1. 1.
    Toward the back or rear; backward.
  2. 2.
    Behind; in the rear.
  3. 3.
    Backward against the mast; -- said of the sails when pressed by the wind.(Naut.)
Phrases & compounds
To be taken aback — To be driven backward against the mast; -- said of the sails, also of the ship when the sails are thus driven.
02 n. An abacus.
  1. 1.
    An abacus.[Obs.]