Spiral \Spi"ral\, n. [Cf. F. spirale. See Spiral, a.]

1. (Geom.) A plane curve, not re["e]ntrant, 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.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Spiral \Spi"ral\, a. [Cf. F. spiral. See Spire a winding line.]

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. (Geom.) 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.

Source: Webster's Revised Unabridged Dictionary (1913)