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.
Spiral
(Spi"ral) n. [Cf. F. spirale. See Spiral, a.]
1. (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.
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.
Spirality
(Spi*ral"i*ty) n. The quality or states of being spiral.
Spirally
(Spi"ral*ly) adv. In a spiral form, manner, or direction.
Spiralozooid
(Spi*ra`lo*zo"oid) n. [Spiral + zooid. So called because they often have a spiral form
when contracted.] (Zoöl.) One of the special defensive zooids of certain hydroids. They have the form
of long, slender tentacles, and bear lasso cells.
Spirant
(Spi"rant) n. [L. spirans, -antis, p. pr. of spirare to breathe. See Spirit.] (Phon.) A term
used differently by different authorities; — by some as equivalent to fricative, - - that is, as including all
the continuous consonants, except the nasals m, n, ng; with the further exception, by others, of the
liquids r, l, and the semivowels w, y; by others limited to f, v, th surd and sonant, and the sound of
German ch, — thus excluding the sibilants, as well as the nasals, liquids, and semivowels. See Guide
to Pronunciation, §§ 197-208.
Spiranthy
(Spi*ran"thy) n. [Gr. a coil + flower.] (Bot.) The occasional twisted growth of the parts of a
flower.
Spiration
(Spi*ra"tion) n. [L. spiratio, fr. spirare to breathe.] The act of breathing. [Obs.] Barrow.
Spire
(Spire) v. i. [L. spirare to breathe. See Spirit.] To breathe. [Obs.] Shenstone.
Spire
(Spire), n. [OE. spire, spir, a blade of grass, a young shoot, AS. spir; akin to G. spier a blade of
grass, Dan. spire a sprout, sprig, Sw. spira a spar, Icel. spira.]