a small, slender, often pointed piece of wood, metal, etc., used to fasten, support, or attach things.

a short, slender piece of wire with a point at one end and a head at the other, for fastening things together.

any of various forms of fasteners or ornaments consisting essentially or partly of a pointed or penetrating wire or shaft (often used in combination)

a jeweled pin.

a badge having a pointed bar or pin attached, by which it is fastened to the clothing

a fraternity pin.

Machinery .

a short metal rod, as a linchpin, driven through holes in adjacent parts, as a hub and an axle, to keep the parts together.

a short cylindrical rod or tube, as a wrist pin or crankpin, joining two parts so as to permit them to move in one plane relative to each other.

a short axle, as one on which a pulley rotates in a block.

the part of a cylindrical key stem entering a lock.

a clothespin.

a hairpin.

rolling pin.

a peg, nail, or stud marking the center of a target.

Bowling . any one of the rounded wooden clubs set up as the target in tenpins, ninepins, duckpins, etc.

Golf . the flag staff which identifies a hole.

any of the projecting knobs or rails on a pinball machine that serve as targets for the ball.

Informal . a human leg.

Music . peg ( def. 5 ) .

Wrestling . a fall.

Nautical .

an axle for a sheave of a block.

belaying pin.

Carpentry . a tenon in a dovetail joint; dovetail.

a very small amount; a trifle

Such insincere advice isn't worth a pin.

Chess . the immobilization of an enemy piece by attacking with one's queen, rook, or bishop.

Electronics . a pin-shaped connection, as the terminals on the base of an electron tube or the connections on an integrated circuit.

to fasten or attach with or as with a pin or pins

to pin two pieces of cloth together.

to hold fast in a spot or position (sometimes fol. by down )

The debris pinned him down.

to transfix or mount with a pin or the like

to pin a flower as a botanical specimen.

Chess . to immobilize (an enemy piece) by placing one's queen, rook, or bishop in a position to check the exposed king or capture a valuable piece if the pinned piece were moved.

Wrestling . to secure a fall over one's opponent. ?

pin down,

to bind or hold to a course of action, a promise, etc.

to force (someone) to deal with a situation or to come to a decision

We tried to pin him down for a definite answer, but he was too evasive for us.

pin in, to fill (gaps in a rubble wall, etc.) with spalls.

pin up, to make (a piece of masonry) level or plumb with wedges. ?

get pinned

(of a young woman) to receive a male student's fraternity pin as a symbol of his affection and fidelity, usually symbolizing that the couple is going steady or plans to become engaged.

(of a young couple) to become formally pledged to one another, though not yet engaged, by the bestowing of such a pin or the exchange of pins.

pin something on someone

Informal . to ascribe the blame or guilt for something to a person; show someone to be culpable

They pinned the crime on him.

pull the pin, Informal . to end a relationship, project, program, or the like, because of lack of continuing interest, success, funds

etc.

verb

detach , unfasten , unlatch , unpin

verb

affix , bind , clasp , close , fasten , fix , hold down , hold fast , immobilize , join , pinion , press , restrain , secure , attach , badge , bolt , brooch , clip , confine , cotter , dart , dowel , fastener , jewelry , ornament , peg , rivet , stake , thole