What does "aback" mean?

Aback: Behind; in the rear. Knolles.

Additional senses

  1. 2.(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.
  2. 3.An abacus. [Obs.] B. Jonson.

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