I tend to call it an engine; to me, it's the more correct term. Why does it matter? It didn't use to, but with more and more electric and hybrid cars, calling an engine a motor, or a motor an engine will only lead to confusion.
Through loose usage, the two terms have become interchangeable, but they really shouldn't be. The word Motor comes from the Latin word: 'movere', meaning: ‘to move’. The 'motor' (as defined) in motorcycle, motorhome, motor sport etc, doesn't refer to an engine, but to motion or movement, just as motor skills doesn't refer to how well you work on engines.
By strict definition: all engines are motors, but not all motors are engines. There is a difference.
