/ ˈsprɒkɪt; NAmE ˈsprɑːkɪt/ noun
1.
(also ˈsprocket wheel ) a wheel with a row of teeth around the edge that connect with the holes of a bicycle chain or with holes in a film, etc. in order to turn it
2.
one of the teeth on such a wheel
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WORD ORIGIN
mid 16th cent. (denoting a triangular piece of timber used in a roof): of unknown origin.