Trembling is a reflex motion caused by cold, fear, or excitement. It can also denote instability.
Often depicted in art with short, wavy motion lines surrounding the outline of the body. (see post #1630828)Sharper, less subtle lines depict twitching, which is more violent and momentary.
Not to be confused with ^^^, which expresses reaction.
The Free Dictionary
The following tags are aliased to this tag:
shiver, shivering, and tremble