pin / pin/ • n. 1. a small piece of metal or wood for fastening or attaching things, in particular: ∎  a thin piece of metal with a sharp point at one end and a round head at the other, used esp. for fastening pieces of cloth. ∎  a small brooch or badge. ∎  Med. a steel rod used to join the ends of fractured bones while they heal. ∎  a metal peg that holds down the activating lever of a hand grenade, preventing its explosion. ∎ short for hairpin. ∎ Mus. a peg around which one string of a musical instrument is fastened.2. a short piece of wood or metal for various purposes, in particular: ∎  (in bowling) one of a set of bottle-shaped wooden pieces that are arranged in an upright position at the end of a lane in order to be toppled by a rolling ball. ∎  a metal projection from a plug or an integrated circuit that makes an electrical connection with a socket or another part of a circuit. ∎ Golf a stick with a flag placed in a hole to mark the hole’s position.3. (pins) inf. legs: she was very nimble on her pins.4. Chess an attack on a piece or pawn, which is thereby pinned: the pin of the black queen by the white rook.• v. (pinned, pin·ning) [tr.] attach with a pin or pins: pin a note on the door. ∎  fasten (something) with a pin or pins in a specified position: her hair was pinned back. ∎  (pin something on) fix blame or responsibility for something on (someone): don’t pin the blame on me. ∎  hold someone firmly in a specified position so they are unable to move: she was standing pinned against the door. ∎  [tr.] transfix (something) with a pin or other pointed instrument: carefully pin the preserved insect specimens to the display surface. ∎  [tr.] Chess hinder or prevent (a piece or pawn) from moving because of the danger to a more valuable piece standing behind it along the line of an attack.PHRASES: (as) neat (or clean) as a pin extremely neat or clean.hear a pin drop used to describe absolute silence.on pins and needles in an agitated state of suspense.pin one's ears back listen carefully.pin one's hopes (or faith) on rely heavily on: retailers were pinning their hopes on a big-spending Christmas.PHRASAL VERBS: pin someone down restrict the actions or movement of an enemy by firing at them. ∎  force someone to be specific and make their intentions clear.pin something down define something precisely.

pin be able to hear a pin drop used to describe absolute silence or stillness.
clean (or neat) as a new pin extremely neat (recorded from the mid 18th century).
for two pins at the slightest provocation (a pin here as the type of something of little worth). Recorded from the late 19th century.
see a pin and pick it up, all the day you'll have good luck; see a pin and let it lie, bad luck you'll have all day proverbial saying, mid 19th century, extolling the virtues of thrift in small matters. A similar idea is found in an older proverb, recorded in Pepys's diary for 2 January 1668 as quoted by Sir William Coventry (1628?–86), ‘He that will not stoop for a pin will never be worth a pound.’

See also how many angels can dance on the head of a pin?, needles and pins at needle, it's a sin to steal a pin.

pin (or PIN) Abbrev. for personal identification number. A number issued to a holder of a magnetic card, for example a credit card or bank card, that the card holder is required to keep secret. Together with the magnetic card the pin acts as an identifier and password to access computer-based services such as ATMs, EPOSs, or EFTS.

pin peg OE.; pointed length of stiff wire used as a fastener XIV; (pl.) legs; skittles XVI. Late OE. pinn, corr. to MLG. pin, (M)LG., (M)Du. pinne (Du. pin), OHG. pfinn (MHG. pfinne), Icel. pinni — L. pinna applied to various objects likened to a wing or feather, of uncert. orig.; cf. penna feather, PEN2.
Hence pin vb. XIV. pincushion XVII. pin-feather immature feather. XVII. pin-money allowance made to a woman for dress, etc., typified by the pins used for fastening or adorning garments. XVII. pin-prick XIX.

PIN / pin/ (also PIN number) • abbr. personal identification number.