Definitions of shaking:

• noun:   the act of causing something to move up and down (or back and forth) with quick movements
• noun:   a shaky motion

  Example: "The shaking of his fingers as he lit his pipe"

• adjective:   vibrating slightly and irregularly; as e.g. with fear or cold or like the leaves of an aspen in a breeze

  Example: "With shaking knees"