n.
1.a movable iron plate that regulates the draft in a stove or chimney or furnace
2.a device that decreases the amplitude of electronic, mechanical, acoustical, or aerodynamic oscillations
3.a depressing restraint
Idiom of the Day
open up on (someone or something)
to attack someone or something, to fire a gun or other weapon at someone or something
The man with the gun opened up on the people on the bus.