The word pin has several meanings:

1. A small, thin piece of metal with a sharp point at one end and a flat or rounded head at the other. Pins hold fabric together while you sew, attach papers to bulletin boards, or keep a name tag on your shirt. Safety pins have a clasp that covers the sharp point so you won't get poked. When something is so quiet you could hear a pin drop, it means the silence is complete and total.
2. To hold something or someone firmly in place. A wrestler might pin an opponent to the mat. You might pin a poster to your wall with thumbtacks.
3. A wooden object that you try to knock down in bowling. Each bowling pin stands at the end of the lane, and a strike means you knocked all ten pins down with one ball.
4. A number you enter to prove who you are, like a PIN code for unlocking your phone or using an ATM card. PIN stands for Personal Identification Number.

Less commonly, a pin can also be a piece of jewelry that fastens to clothing, an important part in machinery that holds things together, or even the stick that marks a hole on a golf course.