In the sense filed here, an e-bike is a small motorbike whose power comes from electricity, not petrol. You ride it as you would a motorbike; the e- tells you the engine is electric. In British English, bike often already means a motorbike, which is why a learner’s dictionary can file the word this way. Though actually, the street and the shops do not fully match that tidy label. In a lot of everyday English — product boxes, news, cycling talk — e-bike much more often means an electric bicycle: it still has pedals, and a motor helps you. An electric motorbike or scooter is then called an electric motorcycle, e-scooter, or, in Taiwan, 電動機車. If you meet the word under “motorbike” in a dictionary, that is the meaning they filed; if you meet it in a shop, look at the picture — pedals or not — before you decide.