What is the meaning of the word "motor"?

Definitions:

a nonspecific agent that imparts motion noun
- Happiness is the aim of all people and the motor of all action.
causing or able to cause motion adjective
- The motor cart travelled along the road.
conveying information to the muscles from the central nervous system adjective
- The motor neurons were damaged by the disease.
machine that converts other forms of energy into mechanical energy and so imparts motion noun
- The motor in the machine spun the cogs.
to travel or be transported in a vehicle verb
- I motored down the highway at top speed.