SCREW Screw, n. Etym: [OE. scrue, OF. escroue, escroe, female screw, F. écrou, L. scrobis a ditch, trench, in LL., the hole made by swine in rooting; cf. D. schroef a screw, G. schraube, Icel. skr.]

1. A cylinder, or a cylindrical perforation, having a continuous rib, called the thread, winding round it spirally at a constant inclination, so as to leave a continuous spiral groove, between one turn and the next, — used chiefly for producing, when revolved, motion or pressure in the direction of its axis, by the sliding of the threads of the cylinder in the grooves between the threads of the perforation adapted to it, the former being distinguished as the external, or male screw, or, more usually the screw; the latter as the internal, or female screw, or, more usually, the nut.

Note: The screw, as a mechanical power, is a modification of the inclined plane, and may be regarded as a right-angled triangle wrapped round a cylinder, the hypotenuse of the marking the spiral thread of the screw, its base equaling the circumference of the cylinder, and its height the pitch of the thread.

2. Specifically, a kind of nail with a spiral thread and a head with a nick to receive the end of the screw-driver. Screws are much used to hold together pieces of wood or to fasten something; — called also wood screws, and screw nails. See also Screw bolt, below.

3. Anything shaped or acting like a screw; esp., a form of wheel for propelling steam vessels. It is placed at the stern, and furnished with blades having helicoidal surfaces to act against the water in the manner of a screw. See Screw propeller, below.

4. A steam vesel propelled by a screw instead of wheels; a screw steamer; a propeller.

5. An extortioner; a sharp bargainer; a skinflint; a niggard. Thackeray.

6. An instructor who examines with great or unnecessary severity; also, a searching or strict examination of a student by an instructor. [Cant, American Colleges]

7. A small packet of tobacco. [Slang] Mayhew.

8. An unsound or worn-out horse, useful as a hack, and commonly of good appearance. Ld. Lytton.