Automatic pistol and Automatic gun

Automatic pistol noun - A pistol that will keep firing until the ammunition is gone or the trigger is released.

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

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

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