The word "automobile" says nothing about the number of wheels. auto = self, mobile = moving. An automobile is a machine that moves under its own power, in other words. A (future) hovercar would still count, and have zero wheels. So yes, a motorcycle is an automobile, as would be a motorised unicycle. The problem is the term "automobile" as used by Americans and almost no-one else. If you mean a CAR, then say so.