noun

1. a peg of wood, metal, etc., used esp. for fastening or holding things together or as a support on which to hang things
2. a little piece of stiff wire with a pointed end and a flattened or rounded head, used for fastening things together or holding them in place; straight pin
3. something worthless or insignificant; trifle
4. a pointed instrument for holding the hair, a hat, etc. in place
5. clothespin, safety pin, cotter pin, etc.
6. anything like a pin in form, use, etc.
7. an ornament, badge, or emblem having a pin or clasp with which it is fastened to the clothing
8. Informal the leg: usually used in pl.
9. Bowling any of the bottle-shaped pieces of wood, or wood coated with plastic, at which the ball is rolled
10. Golf a pole with a flag attached, placed in the hole of a green to mark its location
11. Med. a metal rod used to hold a broken bone together
12. Music any of the pegs for regulating the tension of the strings of a piano, harp, etc.
13. Naut.
    1. thole
    2. any of various pegs or rods used to secure ropes
14. Wrestling fall ()

Etymology: ME pyn < OE pinn, akin to MHG pfinne, a nail, prob. < IE base *bend-, projecting point > MIr benn, peak

transitive verb pinned, pinning pin′·ning

1. to fasten with or as with a pin
2. to pierce with a pin
3. to hold firmly in one place or position
4. ☆ Slang to give one's fraternity pin to, as an informal token of betrothal