from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An instrument used for measuring the pressure of liquids and gases.
- n. A sphygmomanometer.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. An instrument to measure pressure in a fluid, especially a double-legged liquid column gauge used to measure the difference in the pressures of two fluids.
from the GNU version of the Collaborative International Dictionary of English
- n. An instrument for measuring the tension or elastic force of gases, steam, etc., constructed usually on the principle of allowing the gas to exert its elastic force in raising a column of mercury in an open tube, or in compressing a portion of air or other gas in a closed tube with mercury or other liquid intervening, or in bending a metallic or other spring so as to set in motion an index; a pressure gauge. See pressure, and Illust. of air pump.
from The Century Dictionary and Cyclopedia
- n. An instrument for determining and indicating the elastic pressure of gases or vapors.
- n. In physiology, an instrument used for determining blood-pressure.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a pressure gauge for comparing pressures of a gas
 In M. Verne's book a 'manometer' is the instrument used, of which very little is known.
'manometer' is generally known as a pressure gauge.
He also developed numerous other instruments, including the manometer, cyanometer, diaphonometer, anemometer and mountain eudiometer, the first electrometer (1766), a device for measuring electric potential by means of attraction or repulsion of charged bodies, and the first hygrometer, utilizing a human hair to measure humidity (1783).
Finally, the tubes in part F contained a manometer to regulate the rate of air flow.
And there's also some context so you can understand the words better: "Tasha carefully monitored the aneroid manometer," if that one helps you out.
The ‘manometer’ is generally known as a pressure gauge. —
I looked at the manometer; it showed a depth of sixty feet, to which atmospheric heat could never attain.
The log indicated moderate speed, the manometer a depth of about sixty feet.
Soon the Nautilus returned to her native element, and the manometer showed that she was about thirty feet deep.
The compass still showed the course to be E.N.E., the manometer indicated a pressure of five atmospheres, equivalent to a depth of twenty five fathoms, and the electric log gave a speed of fifteen miles an hour.