Definitions of pin:

• noun:   a small slender (often pointed) piece of wood or metal used to support or fasten or attach things
• noun:   a piece of jewelry that is pinned onto the wearer's garment
• noun:   flagpole used to mark the position of the hole on a golf green
• noun:   cylindrical tumblers consisting of two parts that are held in place by springs; when they are aligned with a key the bolt can be thrown
• noun:   informal terms of the leg
• noun:   a club-shaped wooden object used in bowling; set up in groups as a target
• noun:   a holder attached to the gunwale of a boat that holds the oar in place and acts as a fulcrum for rowing
• noun:   axis consisting of a short shaft that supports something that turns
• noun:   a number you choose and use to gain access to various accounts
• noun:   small markers inserted into a surface to mark scores or define locations etc.
• noun:   when a wrestler's shoulders are forced to the mat
• verb:   immobilize a piece
• verb:   attach or fasten with pins
• verb:   pierce with a pin

  Example: "Pin down the butterfly"

• verb:   to hold fast or prevent from moving

  Example: "The child was pinned under the fallen tree"

• name:  A surname (very rare: popularity rank in the U.S.: #26170)