1 pin /ˈpɪn/ noun
plural pins
1 pin
plural pins
Learner's definition of PIN
[count] : a thin, pointed piece of stiff wire with a rounded head at one end that is used especially for fastening pieces of cloth see picture at sewing; see also bobby pin, clothespin, drawing pin, hairpin, safety pin
: a thin, pointed piece of stiff wire with a decoration at one end see also hatpin
chiefly US : brooch
: a small usually circular object that has writing and often a picture on it and that has a pin on the back so that it can be fastened to clothing, bags, etc.
: a thin piece of wood, metal, or plastic that is used for holding things together or for hanging one thing from another
: a long, thin piece of metal that is used to fasten together the ends of broken bone
[count] British : one of the metal pieces that stick out from an electric plug and fit into a socket : prong
[count] : a thin piece of metal that is removed to trigger the explosion of a small bomb (called a grenade)
[count] golf : a long stick with a flag at the top that shows where the hole is on a green
[count] bowling : one of the usually white standing pieces that are knocked down with the ball see also tenpin
pins [plural] informal : the legs of a person or animal

you could hear a pin drop

used to say that it was so quiet that the smallest noise could be heard
2 pin /ˈpɪn/ verb
pins; pinned; pinning
2 pin
pins; pinned; pinning
Learner's definition of PIN
always followed by an adverb or preposition [+ object]
: to fasten or attach (something) with a pin
: to prevent or stop (someone or something) from moving by holding or pressing firmly against something
sometimes used figuratively

pin down

[phrasal verb]
pin (someone) down : to cause or force (someone) to make a definite statement or decision about something
pin down (something) or pin (something) down : to find out (something) with certainty

pin on

[phrasal verb]
pin (something) on (someone) : to say that (something) was done or caused by (someone)
pin (all) your hopes on (something) : to hope very much that (something) will help you or allow you to succeed