set off

verb sets off · setting off · set off

1. idiomatic, intransitive To leave; to set out; to begin a journey or trip. He set off in search of better opportunities.
2. idiomatic, transitive To begin; to cause; to initiate. I had no idea that one simple comment would set off such a huge argument.
3. transitive To cause to begin. When he started giggling, it set us all off too.
4. idiomatic, transitive To cause to explode, let off. What a tragedy, that someone would set off a bomb in a crowded place.
5. idiomatic, transitive To put into an angry mood; to start (a person) ranting or sulking, etc. Don't set him off or he won't shut up all day.
6. idiomatic, transitive To enhance by emphasizing differences. Her plain white dress was set off by a bright red stole.
7. idiomatic, transitive To offset, to compensate for: to reduce the effect of, by having a contrary effect. My taxes did not increase because the amount of my raise was set off by my losses in the stock market.
8. historical To deface or soil the next sheet; said of the ink on a freshly printed sheet, when another sheet comes in contact with it before it has had time to dry.