There is actually a technical definition of "assault weapon", in military terminology, though. It means "anti-tank weapon", i.e. BAZOOKA.
Nobody's advocating for civilian ownership of those.
The "assault weapons" that silly little law bans are indistinguishable, except cosmetically, from a number of civilian firearms it does nothing about. It is an emotionalistic gesture with no meaning and no basis in facts.
Google "Carolyn Mccarthy barrel shroud", sans quotes, for another example of gun-banners' IGNORANCE.