Riding together; being a passenger or sharing a vehicle (car, bike, ship, etc.) with someone else; often used as 'to ride together (同乗する)'.
父の車に同乗して駅まで行った。
I rode with my father in his car to the station.
警察は現場に同乗して証言を聞いた。
A police officer rode along to the scene and took statements.
事故の際、運転手と同乗者が軽いけがをした。
In the accident, the driver and the passenger suffered minor injuries.