PIN DOWN

{v.} 1a. To keep (someone) from moving; make stay in a place or position; trap. * /Mr. Jones' leg was pinned down under the car after the accident./ * /The soldier was pinned down in the hole because rifle bullets were flying over his head./ 1b. To keep (someone) from changing what (he) says or means; make (someone) admit the truth; make (someone) agree to something. * /Mary didn't like the book but I couldn't pin her down to say what she didn't like about it./ * /I tried to pin Bob down to fix my bicycle tomorrow, but he wouldn't say that he could./ 2. To tell clearly and exactly; explain so that there is no doubt. * /The police tried to pin down the blame for the fire in the school./