Meaning of “pin sb down” - Learner’s Dictionary

pin sb down

phrasal verb with pin uk us /pɪn/ verb [ T ] (present participle pinning, past tense and past participle pinned)
DETAILS

to make someone give you details or a decision about something:

I've been trying to get a decision from Jim, but he's very difficult to pin down.
HOLD DOWN

to force someone to stay in a horizontal position by holding them:

They pinned him down on the floor.

(Definition of “pin sb down” from the Cambridge Learner’s Dictionary © Cambridge University Press)