'Spiral operculum' definitions:

Definition of 'Spiral operculum'

From: GCIDE
  • 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. [1913 Webster]
  • 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. [1913 Webster]
  • 3. (Geom.) Of or pertaining to a spiral; like a spiral. [1913 Webster]
  • 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. [1913 Webster]