Involuntarily trembling or shaking, as due to fear, unease, anxiety, or a reaction to (or withdrawal from) a substance, such as drugs or alcohol. I've been doing public speaking for nearly 10 years, but I still get the shakes when I have to get up in front of a packed auditorium. I'm trying to get sober and haven't had a drink in four days, but I've been getting the shakes something fierce.