put the brakes on

• put on the brakes (intransitive only)

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put the brakes on (third-person singular simple present puts the brakes on, present participle putting the brakes on, simple past and past participle put the brakes on)

1. (idiomatic, transitive) To stop (an event, action, or process) or to slow it down.
   • 1903, Frank Norris, “Two Hearts That Beat as One”, in A Deal in Wheat and Other Stories of the New and Old West:

     "[T]he fight I saw that day made the others look like a young ladies' quadrille. . . . [Y]ou could no more separate them two than you could put the brakes on a blame earthquake."

   • 1953 July 6, “The Economy: Loosening Up the Pinch”, in Time, retrieved 31 May 2015:

     Having put the brakes on credit expansion by raising interest rates, Humphrey last week decided the time had come to step on the gas.

   • 2008 January 22, “French court puts brakes on merger of Gaz de France and Suez”, in New York Times, retrieved 31 May 2015:

     A French court on Tuesday put the brakes on the merger of the utilities Gaz de France and Suez.

2. (idiomatic, intransitive) To cease to perform one's current activity or to decrease one's level of activity.
   • 1989 July, Nancy Griffin, “Poetry Man: Robin Williams and Dead Poets Society”, in Premiere Magazine, retrieved 31 May 2015:

     "It would have been so easy for him to have the kids rolling on the floor, doubled up with laughter. So he had to put the brakes on at times."

   • 2011 March 13, John M. Broder, “U.S. Nuclear Industry Faces New Uncertainty”, in New York Times, retrieved 31 May 2015:

     “I think it calls on us here in the U.S., naturally, not to stop building nuclear power plants but to put the brakes on right now until we understand the ramifications of what’s happened in Japan,” Senator Joseph I. Lieberman . . . said.

• (transitive): rein in

• (antonym(s) of “transitive”): speed up,
• (antonym(s) of “intransitive”): speed up, step on the gas

• put on the brakes