Definitions

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

  • adjective Permanently attached or fixed; not free-moving.
  • adjective Stalkless and attached directly at the base.

from The Century Dictionary.

  • In botany, attached without any sensible projecting support; sitting directly on the body to which it belongs without a support; attached by the base: as, a sessile leaf, one issuing directly from the main stem or branch without a petiole or footstalk; a sessile flower, one having no peduncle; a sessile stigma, one without a style, as in the poppy.
  • In zoöl. and anatomy:
  • Seated flat or low; fixed by a broad base; not stalked or pedunculated.
  • Fixed; not free; sedentary.
  • Specifically, in Crustacea: Having no peduncle, as a cirriped; belonging to the Sessilia. Having no stalk or ophthalmite, as an eye.
  • In conchology, having no stalk or ommatophore, as an eye.
  • In entomology, not petiolate, as an abdomen.
  • In Hydroida, not detachable or separable, as a gonophore.

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

  • adjective Attached without any sensible projecting support.
  • adjective (Bot.) Resting directly upon the main stem or branch, without a petiole or footstalk.
  • adjective (Zoöl.) Permanently attached; -- said of the gonophores of certain hydroids which never became detached.

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

  • adjective zoology permanently attached to a substrate; not free to move about; “an attached oyster”
  • adjective botany attached directly by the base; not having an intervening stalk.

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

  • adjective attached directly by the base; not having an intervening stalk
  • adjective permanently attached to a substrate; not free to move about

Etymologies

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

[Latin sessilis, low, of sitting, from sessus, past participle of sedēre, to sit; see sed- in Indo-European roots.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From New Latin sessīlis ("sitting"), from sessus, perfect passive participle of verb sedēre ("sit"), + adjective suffix -īlis. Compare session.

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Examples

  • Perhaps, Richard mused, the sessile is a recording device only, and is incapable of imagination.

    The Garden of Rama Clarke, Arthur C. 1992

  • The ganglia had already finished migrating to three new positions, repeating the same spherical configuration each time, before Richard recognized that what was growing in the sessile was a manna melon.

    The Garden of Rama Clarke, Arthur C. 1992

  • From these lateral stemmed species there is an easy transition to the stemless forms which are sessile, that is, the shelving forms where the pileus is itself attached to the trunk, or other object of support on which it grows.

    Studies of American Fungi. Mushrooms, Edible, Poisonous, etc. George Francis Atkinson 1886

  • They may be sessile, that is, the cup rests immediately on the ground or wood, or leaves, or they may possess a short, or rather long stalk.

    Studies of American Fungi. Mushrooms, Edible, Poisonous, etc. George Francis Atkinson 1886

  • The term _sessilifolius_ has been given to this species of Cytisus, because the leaves are for the most part sessile, that is sit close to the branches, without any or very short footstalks; such they are at least on the flowering branches when the shrub is in blossom, but at the close of the summer they are no longer so, the leaves acquiring very evident footstalks.

    The Botanical Magazine Vol. 8 Or, Flower-Garden Displayed William Curtis 1772

  • Serrated colorectal polyps include the subgroups hyperplastic polyps, sessile serrated polyps (also called sessile serrated adenomas), and serrated adenomas.

    EurekAlert! - Breaking News 2009

  • That alien face - it supposely has a "sessile" compound eye, by which it is meant - not on a stalk.

    April 2010 2010

  • Many ponds are seasonal, lasting just a couple of months (such as sessile pools) while lakes may exist for hundreds of years or more.

    Freshwater biomes 2007

  • Clover is a pair of leaves; the blossom is said to be "sessile" or seated on these leaves.

    Wildflowers of the Farm Arthur Owens Cooke

  • Do legislators imagine that pedophiles are sessile creatures, like sea anemones or Venus fly-traps, and have to wait passively for their victims to come withreach?

    The Volokh Conspiracy » Where, According to Tort Law, Should Accused Criminals and Ex-Convicts Live? 2010

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  • Oxford University Press

    adj. (Biology) permanently attached to a substrate; not free to move about: “an attached oyster”: sesile marine animals and plants”

    monocytes, like all blood cells, are born in the bone marrow and at some point migrate to the spleen, lured by cues yet to be identified. They sit and wait, a sessile bunch, but when aroused by such chemical signatures of damage as angiotensin, the cells surge forth without hesitation

    August 4, 2009

  • "Sessile oak, beech and silver birch crowd around the sandy track, the sunlight twinkles from between the interlocking boughs, the little boys cavort, the adolescents even begin to frolic a bit."

    Psychogeography by Will Self, 154

    Note that the Sessile Oak is a thing unto itself, but in the course of looking it up I looked up the general meaning of "sessile" too.

    October 17, 2010