Spiral

(89), a. [Fr. spiral, Sp. espiral, It. spirale, Lat. as if spiralis, from spira, a coil, a spire. See SPIRE.]

1Sense 1. Winding round a cylinder or other round body, or in a circular form, and at the same time rising or advancing forward; winding like a screw.

2Sense 2. Pointed like a spire, or steeple. [Rare.]

Spiral gear or gearing, gearing consisting of wheels working together with their axes at an angle with each other double that of the direction of the teeth with the axis; — a kind of gearing sometimes used in light machinery instead of bevel gearing, to change the direction of motion. — Spiral wheel (Mach.), a wheel having its teeth cut at an angle with its axis, or so that they form small portions of screws or spirals.

n. (Geom.) A curve described by a point called the generatrix, moving along a straight line according to a mathematical law, while the line is revolving about a fixed point called the pole.

Spiral of Archimedes, a spiral, the law of which is, that the generatrix moves uniformly along the revolving line, which also moves uniformly.