It never did. "Assault weapon" is a catchall term created to cover any high-capacity firearm certain politicians want to restrict.
Assault rifles, as other have mentioned, fire an intermediate power round, and have both semi and fully automatic firing modes.
Battle rifles fire full power rounds, ie 8mm Mauser, 7.62x54mm, .303, 7.62x63mm, etc. They can be bolt-action or self-loading.
Semiautomatic rifles not designed for military use and firing intermediate-level cartridges have no special term to cover the class, though some in recent years have attempted to use terms such as "Urban Carbine" to describe them.
I understand frustration at over-pedantism, but using nonspecific terms created by our enemies is really shortsighted and self-defeating.
John
---------------------------------------------------------------------------Oh- I'm going to the special hell.- Mal Reynolds in Firefly