Definition of pin noun from the Oxford Advanced Learner's Dictionary

noun

pɪn

pɪn

for fastening/joining

1 a short thin piece of stiff wire with a sharp point at one end and a round head at the other, used especially for fastening together pieces of cloth when sewing see also bobby pin, drawing pin, hairpin, linchpin, pins and needles, safety pin

jewellery

2 a short thin piece of stiff wire with a sharp point at one end and an item of decoration at the other, worn as jewellerya diamond pin see also tiepin3 (especially North American English) = brooch

badge

4 (especially North American English) a type of badge that is fastened with a pin at the backHe supports the group and wears its pin on his lapel.

medical

5 a piece of steel used to support a bone in your body when it has been brokenThe pin in her spine will have to be changed as she grows.

electrical

6 one of the metal parts that stick out of an electric plug and fit into a socketa 2-pin plug

in games

7 a wooden or plastic object that is shaped like a bottle and that players try to knock down in games such as bowling

in golf

8 a stick with a flag on top of it, placed in a hole so that players can see where they are aiming forThe ball stopped five feet short of the pin.

legs

9 pins [plural] (informal) a person's legsHe's not as quick on his pins as he used to be.

on small bomb

10 a small piece of metal on a hand grenade that stops it from exploding and is pulled out just before the hand grenade is thrown

for two pins

(old-fashioned, British English) used to say that you would like to do something, even though you know that it would not be sensibleI'd kill him for two pins.For two pins I'd tell her what I really think of her.

more at you could/can hear a pin drop at hear