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Winding or circling round a center or pole and gradually receding from it; as, the spiral curve of a watch spring.

The quality or states of being spiral.

In a spiral form, manner, or direction.

One of the special defensive zooids of certain hydroids. They have the form of long, slender tentacles, and bear lasso cells.

A kind of spiral curve found in certain univalve shells. Agassiz.

Having numerous spiral coils round a center or nucleus; -- said of the opercula of certain shells.

Of or pertaining to the muscles, and taking a spiral course; -- applied esp. to a large nerve of the arm.

Having few spirals, or whorls; as, a paucispiral operculum or shell.

A breathing hole; a vent or ventiduct.

of a seed when it begins to germinate; the plumule in germination; -- so called from its spiral form.

Of a flower, having its parts inserted spirally on the receptacle.

For the latter, see Air chamber. The air vessels of insects are called tracheæ, of plants spiral vessels.

Vascular tissue of plants, consisting of spiral vessels, dotted, barred, and pitted ducts, and laticiferous vessels.

A primary division of gastropods, including those having spiral shells. The two sides of the body are unequally developed.

Changing the direction in the spiral sequence of leaves on a stem.

The spiral tubular proboscis of lepidopterous insects. See Lepidoptera.

channel or groove, like the half of a bean pod. A screw auger has a twisted blade, by the spiral groove of which the chips are discharge.

at the tangents from any point of it to the two circles shall be equal to each other. -- Spiral axis (Arch.), the axis of a twisted column drawn spirally in order to trace the circumvolutions without. -- Axis of abscissas and Axis of ordinates. See Abscissa.

A large spiral marine shell, esp. the common whelk. See Buccinum. [Scot.] Deil's buckie, a perverse, refractory youngster. [Slang]

A genus of land snails having an elongated spiral shell, often of large size. The species are numerous ingabundant in tropical America.