from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun A curve on a plane that winds around a fixed center point at a continuously increasing or decreasing distance from the point.
  • noun A three-dimensional curve that turns around an axis at a constant or continuously varying distance while moving parallel to the axis; a helix.
  • noun Something having the form of such a curve.
  • noun Printing A spiral binding.
  • noun The course or flight path of an object rotating on its longitudinal axis.
  • noun A continuously accelerating increase or decrease.
  • adjective Of or resembling a spiral.
  • adjective Circling around a center at a continuously increasing or decreasing distance.
  • adjective Coiling around an axis in a constantly changing series of planes; helical.
  • adjective Printing Relating to or having a spiral binding.
  • intransitive verb To take a spiral form or course.
  • intransitive verb To rise or fall with steady acceleration.
  • intransitive verb To cause to take a spiral form or course.

from The Century Dictionary.

  • noun A loop in a railroad line used to overcome steep grades in a mountainous region by carrying the line through a continuously rising curve.
  • noun of a point: The origin of coördinates O corresponds to v = o, and the asymptotic points, P′ , P1, round which the curve goes in an ever-closing spiral, correspond to v = ±∞. The intrinsic equation, expressing the relation between the arc σ (measured from O)and the inclination φ of the tangent at any point to the axis of x, is φ = ½πσ.
  • To make spiral; cause to move spirally.
  • To assume a spiral form; move in a spiral course.
  • Of or pertaining to a spire or coil; like a spire; pointed or shaped like a spire.
  • Winding around a fixed point or center, and continually receding from it, like a watchspring; specifically, in conchology, making a number of turns about the columella or axis of the shell; whorled.
  • Winding and at the same time rising or advancing like a screw-thread: more accurately helical or helicoidal.
  • noun In geometry, a plane curve which runs continuously round and round a fixed point, called the center, with constantly increasing radius vector, so that the latter is never normal to the curve; also, a part of such a curve in the course of which the radius from the center describes 360°.
  • noun A helix or curve which winds round a cylinder like a screw.
  • noun A spiral spring.
  • noun In wool, one of the curls or convolutions in wool-fiber, the number of which in a unit of length is made the basis of an estimate of its quality for manufacturing.
  • noun In zoology and anatomy, a spiral formation, as of a univalve, of the cochlea, etc.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Geom.) 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.
  • noun Anything which has a spiral form, as a spiral shell.
  • noun a plane curve which cuts all its generatrices at the same angle. Same as Logarithmic spiral, under Logarithmic.
  • noun a spiral the law of which is that the generatrix moves uniformly along the revolving line, which also moves uniformly.
  • adjective Winding or circling round a center or pole and gradually receding from it.
  • adjective Winding round a cylinder or imaginary axis, and at the same time rising or advancing forward; winding like the thread of a screw; helical.
  • adjective (Geom.) Of or pertaining to a spiral; like a spiral.
  • adjective (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.
  • adjective 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.
  • adjective an operculum whih has spiral lines of growth.
  • adjective any shell in which the whorls form a spiral or helix.
  • adjective See the Note under Spring, n., 4.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun geometry A curve that is the locus of a point that rotates about a fixed point while continuously increasing its distance from that point.
  • noun informal A helix.
  • adjective Helical, like a spiral
  • verb intransitive To move along the path of a spiral or helix.
  • verb figuratively, intransitive To increase continually.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun a structure consisting of something wound in a continuous series of loops
  • noun a curve that lies on the surface of a cylinder or cone and cuts the element at a constant angle
  • noun a plane curve traced by a point circling about the center but at increasing distances from the center
  • noun ornament consisting of a curve on a plane that winds around a center with an increasing distance from the center
  • adjective in the shape of a coil
  • verb to wind or move in a spiral course


from The American Heritage® Dictionary of the English Language, 4th Edition

[Medieval Latin spīrālis, of a spiral, from Latin spīra, coil; see spire.]


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