interrupted screw

American  

noun

1. a screw having the thread interrupted in one or more places by longitudinal channels, as in the breech of a cannon or the lead screw of a lathe.

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interrupted screw British  

noun

1. a screw with a slot or slots cut into the thread, esp one used in the breech of some guns permitting both engagement and release of the block by a partial turn of the screw

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