American informal to think about or state something in an exact way
Before you argue with him, button down the specific points you want to make.
button down
To fasten or secure something in place with buttons. A noun or pronoun can be used between "button" and "down." Button down your pocket so that nothing falls out of it.Button that flap down so it doesn't get blown around by the wind.
button something down
to fasten something down with buttons. Button your collar down. You look too casually dressed.Please button down your collar.