All of you are wrong! Assault Rifle is not a made up term.
The German MP 44, also known as the StG 44, was called the
Sturmgewehr by the German military, which translates to "Assault Rifle". Allegedly, Adolf Hitler himself coined the term (not a lot to back that up).
Assault rifles are real. They are military grade small arms that combine the roles of carbine, submachine gun, and automatic rifles. The key part of the definition is that it is a select fire weapon, capable of both full auto and semi automatic fire. An M16/M4 is an assault rifle. An AR15 is not.