- An abacus.
- Towards the back or rear; backwards.
- In the rear; a distance behind. <ref name=SOED/>
- By surprise; startled; dumbfounded.
- 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. <ref name=SOED/>
- By setting the foresail aback and the headsail in the middle one can bring a fore-and-aft rigged sailing boat practically to a halt even in heavy wind.
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