Sidecar

An NSU Motorenwerke 601 motorcycle from the 1930s fitted with a Steib Metallbau sidecar

A sidecar is a one-wheeled device attached to the side of a motorcycle, scooter, or bicycle, making the whole a three-wheeled vehicle. The combination of a motorcycle with a sidecar is sometimes called a hack, outfit, rig, tricycle, or tuk-tuk.