Idiom
pin down someonepin down (someone)
1.
to keep someone from being able to escape by shooting at them.
For a time, the crew was pinned down by machine-gun fire.
2.
to get specific information from someone.
It is not easy to pin down a politician who won't even tell you if it's raining or snowing!We tried to pin him down on where the money would come from.
3.
to hold someone by force so that they cannot move.
Burns usually pinned down and then handcuffed his victims.I was pinned down by a wall that had fallen.
Usage notes: when the object is a pronoun, it always follows pin:
Don't pin me down about my plans.