The curved bar connected by a shaft to the front wheel of a bicycle or motorcycle, positioned nearly horizontally in front of the rider's seat, designed to be gripped by the rider while riding, and used to steer the vehicle. Usually used in the plural; as, don't let go of the handlbars.

the shaped bar used to steer a bicycle

A tube that can be of various materials and shapes and used to aid in steering. You hold on to them.

The flat or riser bar that grips, brake levers, and shifters are attached to.

rod or bar with handle at each end.

Handlebars usually refer to the steering mechanism for bicycles and motorcycles; the equivalent of a steering wheel, though used in conjunction with the rider's balance or center of gravity to steer.