(1) To move something with an irregular, rapid, violent action. (2) To stir up or excite.
Example:
Philip found Louisa highly agitated at the news of her son's disappearance.
Agitate can mean to shake or stir something physically, but more often its meaning is emotional or political. Agitation for a cause -- a new union, civil rights, a change of government -- involves talking it up, passing out information, and holding meetings, though sometimes as secretly as possible. An agitated person or animal usually feels severely anxious and upset, not pleasantly excited.