vacuum

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Absence of matter.
2. n. A space empty of matter.
3. n. A space relatively empty of matter.
4. n. A space in which the pressure is significantly lower than atmospheric pressure.
5. n. A state of emptiness; a void.
6. n. A state of being sealed off from external or environmental influences; isolation.
7. n. A vacuum cleaner.
8. adj. Of, relating to, or used to create a vacuum.
9. adj. Containing air or other gas at a reduced pressure.
10. adj. Operating by means of suction or by maintaining a partial vacuum.
11. v. To clean with or use a vacuum cleaner.

Century Dictionary and Cyclopedia

1. n. Empty space; space void of matter: opposed to plenum; in practical use, an inclosed space from which the air (or other gas) has been very nearly removed, as by an air-pump. The metaphysicians of Elea, Parmenides and Melissus, started the notion that a vacuum was impossible, and this became a favorite doctrine with Aristotle. All the scholastics upheld the maxim that “nature abhors a vacuum.” This is the doctrine of the plenists. Atomism, on the other hand, carried out in a thoroughgoing manner, supposes empty space between the atoms. That gases do not fill space homogeneously is now demonstrated by the phenomena of transfusion and by the impulsion of Crookes's radiometer; while the other observed facts about gases, taken in connection with these, render some form of the kinetical theory of gases almost certain. This supposes the molecules of gases to be at great distances from one another as compared with their spheres of sensible action. This, however, does not exclude, but rather favors, Boscovich's theory of atoms—namely, that atoms are mere movable centers of potential energy endowed with inertia; and this theory makes each atom extend throughout all space in a certain sense. But this does not constitute a plenum, for a plenum is the exclusive occupation of each part of space by a portion of matter. It may be said that the spaces between the atoms are filled by the luminiferous ether, which seems to be the substance of electricity; but the dispersion of light by refraction seems to show that the ether itself has a molecular structure. A vacuum, in the sense of a space devoid of ordinary ponderable matter, is produced (more or less perfectly) when the air is removed from an inclosed space, such as the receiver of an air-pump, a part of a barometric tube, etc. In the receiver of the ordinary airpump the vacuum can only be partial, since with each stroke of the piston only a certain fraction of the air is removed (depending upon the relative size of the cylinder and the receiver), and hence, theoretically, an infinite number of strokes would be necessary. Practically, the degree of exhaustion obtained falls short of that demanded by theory, owing to the imperfections of the machine; thus, in the common form, the exhaustion is limited to the point where the remaining air has not sufficient elasticity to raise the valves. By the Sprengel or mercury air-pump a much more perfect degree of exhaustion is attainable than with the mechanical form. (See mercury air-pump, under mercury.) The most perfect vacuum is obtained when chemical means are employed to absorb the last traces of gas left in the receiver exhausted by the mercury airpump. The Torricellian vacuum—that is, the space above the mercury in a carefully manipulated barometer-tube—is more nearly perfect in this respect, but the space contains a small amount of the vapor of mercury. See Torricellian.

Wiktionary

1. n. A region of space that contains no matter.
2. n. A vacuum cleaner.
3. v. transitive To clean (something) with a vacuum cleaner.
4. v. intransitive To use a vacuum cleaner.

GNU Webster's 1913

1. n. (Physics) A space entirely devoid of matter (called also, by way of distinction, absolute vacuum); hence, in a more general sense, a space, as the interior of a closed vessel, which has been exhausted to a high or the highest degree by an air pump or other artificial means.
2. n. The condition of rarefaction, or reduction of pressure below that of the atmosphere, in a vessel, as the condenser of a steam engine, which is nearly exhausted of air or steam, etc..

WordNet 3.0

1. n. the absence of matter
2. v. clean with a vacuum cleaner
3. n. a region that is devoid of matter
4. n. an electrical home appliance that cleans by suction
5. n. an empty area or space