From The Collaborative International Dictionary of English v.0.48:
Astern \A*stern"\, adv. [Pref. a- + stern.] (Naut.)
1. In or at the hinder part of a ship; toward the hinder
part, or stern; backward; as, to go astern.
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2. Behind a ship; in the rear. "A gale of wind right astern."
--De Foe. "Left this strait astern." --Drake.
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To bake astern, to go stern foremost.
To be astern of the reckoning, to be behind the position
given by the reckoning.
To drop astern, to fall or be left behind.
To go astern, to go backward, as from the action of
currents or winds.
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