Definitions

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

  • n. A ringlike figure, part, structure, or marking, such as a growth ring on the scale of a fish.
  • n. A ring or group of thick-walled cells around the sporangia of many ferns that functions in spore release.
  • n. The ringlike remains of a broken partial veil, found around the stipes of certain mushrooms.
  • n. Mathematics The figure bounded by and containing the area between two concentric circles.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A ring- or donut-shaped area or structure.
  • n. The region in a plane between two concentric circles of different radius.
  • n. Any topological space homeomorphic to the region in a plane between two concentric circles of different radius.
  • n. The ring of the sun not covered by the moon in an annular solar eclipse.
  • n. Structure in a fern that consists of differentially thick-walled cells on a sporangium that bend and distort as a result of drying.
  • n. The membranous remnants of a partial veil which leaves a ring on the stem of a mushroom.
  • n. The space contained between the centre well bore and any external tubing. Sometimes used for separated gas flow.

from the GNU version of the Collaborative International Dictionary of English

  • n. A ring; a ringlike part or space.
  • n.
  • n. A space contained between the circumferences of two circles, one within the other.
  • n. The solid formed by a circle revolving around a line which is the plane of the circle but does not cut it.
  • n. Ring-shaped structures or markings, found in, or upon, various animals.

from The Century Dictionary and Cyclopedia

  • n. A ring-like space or area contained between the circumferences of two concentric circles.
  • n. In anatomy, a ring-like part, opening, etc.: used in Latin phrases.
  • n. (See below.) In botany: The elastic ring which surrounds the spore-case of most ferns.
  • n. In mosses, an elastic ring of cells lying between the lid and the base of the peristome or orifice of the capsule.
  • n. In fungi, the slender membrane surrounding the stem in some agarics after the cap has expanded.
  • n. In zoology: A thin chitinous ring which encircles the mantle in the Tetrabranchiata, connecting chitinous patches of the mantle into which the shell-muscles are inserted.
  • n. In entomology, a narrow encircling band, generally of color; sometimes a raised ring.
  • n. In astronomy, the ring of light seen about the edge of the moon in an annular eclipse of the sun. See annular eclipse, under annular.
  • n. In the Equisetaceæ, the sheath below the spike formed by the union of the bases of the leaves.
  • n. In diatoms, the rim of silex formed within the frustules of some genera.
  • n. The fleshy rim of the corolla in milkweeds.
  • n. One of the external subdivisions of the body of a leech, resembling a segment of the body of an earthworm.

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

  • n. a toroidal shape
  • n. (Fungi) a remnant of the partial veil that in mature mushrooms surrounds the stem like a collar

Etymologies

Latin ānulus, ring, diminutive of ānus.
(American Heritage® Dictionary of the English Language, Fourth Edition)

Examples

  • One of the biggest variables is whether the area called the annulus, which is between the inner piping and the outer casing, has sprung an oil leak.

    ajc.com - News

  • One of the biggest variables on the static kill's finality is whether the area called the annulus, which is between the inner piping and the outer casing, has sprung an oil leak.

    CBS 4 - South Florida's Source for Breaking News, Weather, and Sports

  • BP Senior Vice President Kent Wells said it's "really a possibility" that cement that engineers pumped in through the top went down into the reservoir, came back up and plugged the annulus, which is between the inner piping and the outer casing.

    Storms delay completion of relief well to seal damaged BP oil well in gulf

  • U.S. officials are concerned that the flooding of that area, known as the annulus, could compromise a cement plug that the company installed in early August at the top of the well.

    Weather Delays Progress at Well Site

  • No one is sure if the oil and gas are flowing inside the pipe or outside the casing in what is called the annulus -- the space between the pipe and the rock wall of the hole.

    BP aims to plug gulf oil well for good with two-pronged 'kill' shot

  • U.S. officials were concerned that the injection of liquid into the gap between the well and the rock known as the annulus could compromise a cement plug that BP cast at the top of the well in early August, letting some oil escape into the ocean.

    BP to Push Ahead on Replacing Blowout Preventer

  • There is one scenario, not considered likely, in which hydrocarbons would be lurking in the space known as the annulus, between the casing and the rock wall of the well bore, said retired Coast Guard Adm. Thad Allen, the national incident commander.

    BP to test oil well for hydrocarbons during break in drilling relief well

  • The former constitutes, according to Sir John Herschel's views, an annulus, that is to say, an independent zone, somewhat remote from our lenticular-shaped starry stratum, and similar to Saturn's ring.

    COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1

  • BP Senior Vice President Kent Wells said it's "really a possibility" that cement engineers pumped in through the top went down into the reservoir, came back up and plugged the annulus, which is between the inner piping and the outer casing.

    Smoky Mountain News

  • Teams first will drill into the outermost wall of the Macondo wellbore, known as the annulus, that encircles the round steel casing at the center of the well.

    chron.com Chronicle

Comments

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  • My thoughts exactly.

    August 5, 2010

  • This word, to me at least, is disconcerting in its vague seaminess.

    August 4, 2010

  • “If it only fills the center well pipe, and not the area called the annulus between the inner piping and the outer casing, then a final cementing of the well may have to wait another few weeks.”

    The New York Times, BP Begins ‘Static Kill,’ to Seal Well Permanently, by Cliffor Klaus, August 3, 2010

    August 4, 2010

  • "Victoria hurried to the door. She arrived and stared down at the doorknob, apparently perplexed. Langdon arrived behind her and eyed the peculiar donut-shaped hoop hanging where the doorknob should have been.
    'An annulus,' he whispered. Langdon reached out and quietly lifted the ring in his hand. He pulled the ring toward him. The fixture clicked."
    - 'Angels and Demons', Dan Brown.

    February 28, 2008