According to the FBI, the ATF, and other law enforcement agencies...the people who know best what these weapons are capable of.  
Certainly definitions can change...but labeling a semi-automatic rifle an assault rifle because it looks the same is like calling a stock Doge Charger a super car just because it has the same shape as a Hellcat.  The capabilities of one is mild when compared to the other.  
An assault rifle is capable of fully automatic fire.  Period.  Every other rifle ever produced is a semi-automatic rifle no matter how scary, or how innocuous, it might look.  There must be a reason why the media created the term "assault weapon" (assault rifle already had a legal definition).  Any ideas what that reason might be and why they continue to misuse the phrase assault rifle?