1. To fix or fasten something to something else with a pin or similar fastener. A noun or pronoun is used between "pin" and "to." I pinned the poster to the notice board in the common area of the campus. We'll need to pin the tent down with stakes.

2. To shove someone or something up against something else and forcefully hold them or it in place. A noun or pronoun is used between "pin" and "to." The car slammed into the tree and pinned it to the side of the building. The bully pinned me to the wall, demanding I give him my lunch money.