tremble tremble /ˈtrɛmbəl/

noun

1. A reflex motion caused by cold, fear or excitement  ( shake , tremble , shiver )
   a reflex motion caused by cold, fear or excitement
   

verb

1. () Move or jerk quickly and involuntarily up and down or sideways  ( tremble )
   move or jerk quickly and involuntarily up and down or sideways
    His hands were trembling when he signed the document
   His hands were trembling when he signed the document