Legal and technical term for motorcycles with an engine displacement of 50cc or larger, as defined under Japanese vehicle classification. In everyday speech, バイク is more common.
To get a motorcycle license, you need to attend a driving school.
This parking lot is for motorcycles only.
Compound of 自動 (じどう, 'automatic') and 二輪 (にりん, 'two wheels'), literally 'automatic two-wheeler'.