A complainer; one who speaks out when there are problems. Often used pejoratively. / Of several problems, the most apparent or the most urgent.

On a steam locomotive, an unpowered wheel located in front of the driving wheels.

(rail transport) On a steam locomotive, a powered wheel driven by the locomotive's pistons or turbine.

(rail transport) On a steam locomotive, an unpowered wheel or axle located behind the driving wheels.

A device locked to the wheel of a motor car to prevent it from being driven; normally used to enforce payment of a traffic violation fine

a revolving crib set in the wall of a church or convent, allowing an abandoned baby to be left anonymously and safely.

A symbol of indigenous North American culture and religion. / A stone monument related to this symbol, constructed by laying stones in a particular pattern on the ground oriented to the four directions.

(circus) A hollow wheel larger than a person, attached to and suspended from an axle, and inside of which an artist performs.

A device for measuring distance, consisting of a wheel of fixed circumference, a handle, and a clicking device triggered by each revolution of the wheel.

A gear wheel that revolves around the wheel with which it meshes, in an epicyclic train.