Definitions

Turn: 

- To cause to move around an axis or center; cause to rotate or revolve.

- To cause to move around in order to achieve a result, such as opening, closing, tightening, or loosening.

- To alter or control the functioning of (a mechanical device, for example) by the use of a rotating or similar movement.

- To revolve in the mind; meditate on; ponder.

- To change the purpose, intention, or content of by persuasion or influence

- To change the order or disposition of; unsettle.

- To cause to take on a specified character, nature, identity, or appearance; change or transform. 

- To make sour; ferment.

(thefreedictionary.com)