What is the meaning of Pinion?

A wing.

The joint of a bird's wing farthest from the body.

Any of the outermost primary feathers on a bird's wing.

A moth of the genus Lithophane.

To cut off the pinion of a bird’s wing, or otherwise disable or bind its wings, in order to prevent it from flying.

To bind the arms of someone, so as to deprive him of their use; to disable by so binding.

To restrain; to limit.

The smallest gear in a gear train.

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gearwheel

Source: wiktionary.org