set off

Verb

set off (third-person singular simple present sets off, present participle setting off, simple past and past participle set off)

1. (idiomatic, intransitive) To leave; to set out; to begin a journey or trip.
   • He set off in search of better opportunities.
   • Considerable excitement was caused on the L.M.S.R. Aberdeen line out of Perth recently when a shunting engine in Perth North goods yard, whose driver and fireman were absent, was accidentally set in motion by a shunter and set off unattended on to the main line.1941 October, “Notes and News: A Highland Runaway”, in Railway Magazine, page 469

   Synonyms:

   set forth, take off, 23 skidoo, beat it, bug off, remove, egress, bugger off, book, bounce

2. (idiomatic, transitive) To begin; to cause; to initiate.
   • I had no idea that one simple comment would set off such a huge argument.

   Synonyms:

   bring forth, produce, cause, contrive, create, ferment, forge, develop, engender, evolve

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.
   • Wrex: There are acid tanks rigged up on that thing. Set them off. Millions of my ancestors died to put these things down. Don't let them come back.2008, BioWare, Mass Effect (Science Fiction), Redwood City: Electronic Arts, →ISBN, →OCLC, PC, scene: Secure Lab, Rift Station, Noveria

   Synonyms:

   blow up, detonate, touch off

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.

   Synonyms:

   incense, put out, affront, aggravate, anger, antagonize, awrath, burn up, cheese off, cross

6. (idiomatic, transitive) To enhance by emphasizing differences.
   • Her plain white dress was set off by a bright red stole.
   • And then one afternoon in the hinder end of April came young Heriotside riding to the Skerburnfoot. His arm was healed, he had got him a fine new suit of green, and his horse was a mettle beast that well set off his figure.1902, John Buchan, The Outgoing of the Tide
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.
   • When a woman had made such a mistake, there was only one way to repair it,—to accept it. One folly was enough, especially it was to last for ever; a second one would not much set it off.1908, Henry James, chapter XXXIX, in The Portrait of a Lady (The Novels and Tales of Henry James), New York edition, volume (please specify |volume=I or II), Boston, Mass.; New York, N.Y.: Charles...

   Synonyms:

   counter, counteract, negate, offstand

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.