How do you spell Trembling

Available Definitions:
1)  a. - Shaking; tottering; quivering.
2)  v. i. - To totter; to shake; -- said of a thing.
3)  v. i. - To quaver or shake, as sound; to be tremulous; as the voice trembles.
4)  n. - An involuntary shaking or quivering.