aback

/əˈbæk/
/əˈbæk/
/əˈbæk/

adverb

  1. Towards the back or rear; backwards.

  2. In the rear; a distance behind.

  3. By surprise; startled; dumbfounded. (see usage)

  4. Backward against the mast; said of the sails when pressed by the wind from the "wrong" (forward) side, or of a ship when its sails are set that way.

noun

  1. An abacus.