Unsteady
Part of speech: verb
Definition: To render unsteady, removing balance.
Part of speech: adjective
Definition: Not held firmly in position. Noted for lack of regularity or uniformity. Inconstant in purpose, or volatile in behaviour.
Trembling
Part of speech: verb
Definition: To shake, quiver, or vibrate.
Example sentence: I had a voice - I had an instrument - I loved singing and I had an inspired singing teacher, Miss Sleigh. I went to her every Saturday, and I now possess the upright Steinway piano beside which I used to stand in fear and trembling if I hadn't done my breathing exercises.