A chain or ring to which a key may be attached(noun)
An ornamental piece holding such a chain or ring.(noun)
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Use "keychain" in a sentence
"While tons of items fit into this category, one that caught my eye is the Piranha from PocketToolX, which specializes in what I call keychain multitools."
"The advantage to this type of keychain is that it is very easy to quickly add and remove items from the ring"
"The part that really made me laugh was the fact that they called a keychain made out of a spent .50 shell casing that had been drilled and rendered useless "ammunition.""