pin vs unpin

pin is a noun but unpin is not a noun.

Word	Noun	Adjective	Verb	Adverb
pin	Yes	No	Yes	No
unpin	No	No	Yes	No

pin (noun)	unpin (noun)
a small slender (often pointed) piece of wood or metal used to support or fasten or attach things
a piece of jewelry that is pinned onto the wearer's garment
axis consisting of a short shaft that supports something that turns
a holder attached to the gunwale of a boat that holds the oar in place and acts as a fulcrum for rowing
a club-shaped wooden object used in bowling; set up in triangular groups of ten as the target
flagpole used to mark the position of the hole on a golf green
cylindrical tumblers consisting of two parts that are held in place by springs; when they are aligned with a key the bolt can be thrown
informal terms for the leg
small markers inserted into a surface to mark scores or define locations etc.
when a wrestler's shoulders are forced to the mat

pin (verb)	unpin (verb)
(chess) immobilize a piece	remove the pins from; unfasten the pins of
attach or fasten with pins
pierce with a pin
to hold fast or prevent from moving