Automatic rifle and Automatic weapon

Automatic rifle noun - Light machine gun.

Automatic weapon and automatic rifle are semantically related. In some cases you can use "Automatic weapon" instead a noun phrase "Automatic rifle".

Automatic weapon noun - A firearm that reloads itself and keeps firing until the trigger is released.

Automatic rifle and automatic weapon are semantically related. Sometimes you can replace phrase "Automatic rifle" with "Automatic weapon", this phrases are similar.