The Collaborative International Dictionary of English v.0.48:
Spiral \Spi"ral\, a. [Cf. F. spiral. See Spire a winding
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
Spiral operculum, an operculum whih has spiral lines of
Spiral shell, any shell in which the whorls form a spiral
Spiral spring. See the Note under Spring, n., 4.