tremble

verb

• shake involuntarily, typically as a result of anxiety, excitement, or frailty:Isobel was trembling with excitement
• be in a state of extreme apprehension: [with infinitive]:I tremble to think that we could ever return to conditions like these
• shake or quiver slightly:the earth trembled beneath their feet

noun

• 1a trembling feeling, movement, or sound:there was a slight tremble in his voice

• 2 (the trembles) informal a physical or emotional condition marked by trembling.
• another term for milk sickness.