pin has 16 distinct synonyms spread across 10 of its 15 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is unpin.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a piece of jewelry that is pinned onto the wearer's garment
a number you choose and use to gain access to various accounts
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
flagpole used to mark the position of the hole on a golf green
a club-shaped wooden object used in bowling; set up in triangular groups of ten as the target
to hold fast or prevent from moving
“The child was pinned under the fallen tree”
attach or fasten with pins
“pin the needle to the shirt”
Synonyms, antonyms and the broader and narrower relations for pin come from Princeton University’s WordNet. Full sources and licences.