The first definition of screw in the dictionary is a device used for fastening materials together, consisting of a threaded and usually tapered shank that has a slotted head by which it may be rotated so as to cut its own thread as it bores through the material. Other definition of screw is Also called: screw-bolt. a threaded cylindrical rod that engages with a similarly threaded cylindrical hole; bolt. Screw is also a thread in a cylindrical hole corresponding with that on the bolt or screw with which it is designed to engage.