shell


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Related to shell: shell shock, Shell scripting

shell

(shel),
An outer covering.
Farlex Partner Medical Dictionary © Farlex 2012

shell

(shel)
An outer covering.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

shell

any hard outer covering, such as the carapace of turtles and tortoises, the exoskeleton of crustaceans, the calcareous plates of echinoderms, the outermost membranes of an egg, the skeleton of Foraminifera or the mantle secretions of molluscs.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

impression, eye

A negative form or replica of the anterior part of the eye. A substance with rapid gelling properties is held in contact with the eye until gelled. This impression (or mould) is then used in the preparation of a positive model called a cast (or casting) of the anterior part of the eye: it is made by filling the impression with a material containing a plaster of Paris base which hardens to artificial stone. Using this cast a shell of a scleral contact lens is produced with optimum shape of the back surface. Syn. impression; impression moulding; mould; ocular impression.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in classic literature ?
Only a few grass houses had been damaged by the shells. Only a few coconuts had been chopped down.
From recent sea-shells being found on two of the higher step-formed plains, which must have been modelled and upraised before the mud was deposited in which the Macrauchenia was entombed, it is certain that this curious quadruped lived long after the sea was inhabited by its present shells. I was at first much surprised how a large quadruped could so lately have subsisted, in lat.
The light disclosed the frightful injury which a fragment of the shell had inflicted on the Englishwoman's head.
the problem of human destiny disgusts me." He turned from the bed, and illustrated his disgust by spitting on the fragments of the exploded shell. "We must leave her there," he resumed.
Bewildered by the noise, panic-stricken as the danger from the shells threatened the cottage more and more nearly, Grace threw her arms round the nurse, and clung, in the abject familiarity of terror, to the woman whose hand she had shrunk from touching not five minutes since.
Hardly had the shell been opened when the cat leaped out, slightly bruised, but full of life, and exhibiting no signs whatever of having made an aerial expedition.
Soon the nature of the soil changed; to the sandy plain succeeded an extent of slimy mud which the Americans call "ooze," composed of equal parts of silicious and calcareous shells. We then travelled over a plain of seaweed of wild and luxuriant vegetation.
We have evidence in the loess of the Rhine of considerable changes of level in the land within a very recent geological period, and when the surface was peopled by existing land and fresh-water shells. The wide difference of the fish on opposite sides of continuous mountain-ranges, which from an early period must have parted river-systems and completely prevented their inosculation, seems to lead to this same conclusion.
Some species of fresh-water shells have a very wide range, and allied species, which, on my theory, are descended from a common parent and must have proceeded from a single source, prevail throughout the world.
It is just possible that this hill is Mount Ararat, and that Noah's Ark rested here, and he ate oysters and threw the shells overboard.
Simply at the point I started from, namely, those oyster shells are there, in regular layers, five hundred feet above the sea, and no man knows how they got there.
North America and European market are expected to witness a steady growth in the demand for almond with shell snack over the forecast period.