noun
Formal or legal term for a motorcycle with an engine displacement of 50cc or larger, as opposed to a moped (原動機付自転車). In everyday conversation, バイク is more common.
自動二輪車の免許を取るには教習所に通う必要がある。
To get a motorcycle license, you need to attend a driving school.
この駐車場は自動二輪車も利用できます。
This parking lot can also be used by motorcycles.