1. Stern foremost or backward
   "the steamer went astern at half speed"
    
2. At or near or toward the stern of a ship or tail of an aeroplane
   "the captain looked astern to see what the fuss was about";
   - aft, abaft
    
3. (of a ship or an aeroplane) behind
   "we dropped her astern on the end of a seven-inch manilla, and she laid comfortably on the ebb tide"

Encyclopedia: Astern