Spiral

Part of speech: noun (n.)

1. A plane curve, not reëntrant, 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. Cf. Helix.

2. Anything which has a spiral form, as a spiral shell. Equiangular spiral,a plane curve which cuts all its generatrices at the same angle. Same as Logarithmic spiral, under Logarithmic. -- Spiral of Archimedes, a spiral the law of which is that the generatrix moves uniformly along the revolving line, which also moves uniformly.

Part of speech: adjective (a.)

1. Winding or circling round a center or pole and gradually receding from it; as, the spiral curve of a watch spring.

2. Winding round a cylinder or imaginary axis, and at the same time rising or advancing forward; winding like the thread of a screw; helical.

3. Of or pertaining to a spiral; like a spiral. Spiral gear, or Spiral wheel (Mach.), a gear resembling in general a spur gear, but having its teeth cut at an angle with its axis, or so that they form small portions of screws or spirals. -- Spiral gearing, a kind of gearing sometimes used in light machinery, in which spiral gears, instead of bevel gears, are used to transmit motion between shafts that are not parallel. -- Spiral operculum, an operculum whih has spiral lines of growth. -- Spiral shell, any shell in which the whorls form a spiral or helix. -- Spiral spring. See the Note under Spring, n., 4.