Definition of "kick in" [kick in]

• To kick or strike so as to cause the object struck to collapse or fall inwards. (verb)
• To start or connect suddenly. (verb)
• To contribute, especially to a collection of money. (verb)

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• "Shelley's words were a kick in the stomach that made the twin-tub sensation feel like minor indigestion."
• "We're already seeing inflation start to flare, some of the recent commodities activity, and I just--I'm hoping that Mr. Obama's re-election ambitions kick in here and he says, I need to get this unemployment growth down, and also it's not going to help me if we've got $5-a-gallon gasoline next year, so forget the stimulus, forget the monetary creation."
• "‘It was at night … You couldn’t see a thing … We were separated … There were shots and shouting and chases … I was hit in the chest and I started to run … A couple of cops grabbed me … I bit one of them and forced the other to let go with a kick in the guts …"