A phrase that consists of a verb with a preposition or adverb or both, the meaning of which is different from the meaning of its separate parts.
Phrasal Verb:
set someone off
Meaning / Example:
1. to cause someone to become very angry; to ignite someone's anger. > That kind of thing really sets me off! > Your rude behavior set off Mrs. Franklin.
2. to cause someone to start talking or lecturing about a particular subject. > When I mentioned high taxes it really set Walter off. He talked and talked.