Adding to what user wl already said - 'assault rifle' is a really vague term, but historically it is defined as a rifle that soldier can use to provide a coveri

Adding to what user wl already said - 'assault rifle' is a really vague term, but historically it is defined as a rifle that soldier can use to provide a covering fire to himself while assaulting an enemy position. Before first 'assault rifles' appeared comrade soldiers where supposed to provide suppressive fire during an attack. And from that definition it is clear that semi-auto weapon cannot be considered an 'assault rifle'.