What is a carbine assult rifle?

All carbines are rifles; but, not all rifles are carbines. (Got it?) Generally speaking, a carbine is a rifle characterized by any or all of the following features: A shorter barrel, lighter weight, or shorter stock. A, 'carbine assault rifle' fits this definition; however, the Army's M4 is technically an, 'assault carbine'. Only the most academically correct definition would use the phrase, 'rifle carbine'.