1. 向艉部（或机尾）；在艉部（或机尾）
If you go aft in a boat or plane, you go to the back of it. If you are aft, you are in the back.

2. 艉部的；后部的
The aft end on a boat or plane is towards the back of it.

1. at or near or toward the stern of a ship or tail of an airplane

e.g. 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

Synonym: abaftastern