Backward against the mast; -- said of the sails when pressed by the wind.

The situation of sails when the wind is caught on the forward surface causing causing them to be pressed aft against the mast. This may cause the ship to go astern.

The set of a boat's sails with the wind on the leeward instead of the windward side

An abacus.

by surprise; "taken aback by the caustic remarks"

Toward the back or rear; backward.

Behind; in the rear.