What is the meaning of astern?

adverb

• Stern foremost or backward.
  • usage: "the steamer went astern at half speed"
• At or near or toward the stern of a ship or tail of an airplane.
  • usage: "stow the luggage aft"; "ships with square sails sail fairly efficiently with the wind abaft"; "the captain looked astern to see what the fuss was about"
  • synonyms: aft, abaft
• Of a ship or an airplane. ( behind)
  • usage: "we dropped her astern on the end of a seven-inch manilla, and she laid comfortably on the ebb tide"