Manometer 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.

Example:
How to relate acceleration and height difference in a u-tube Manometer?

Taxonomy
pressure, gauges, measure, gas, liquid, Torr, manometer, Pressure gauges, vacuum, fluid, diaphragm, measurement, atmospheric pressure, gauge pressure, hot cathode, Bourdon tube, instruments, electrons.

Defination from the web:
manometer could also be referring to a pressure measuring instrument, usually limited to measuring pressures near to atmospheric. The term manometer is often used to refer specifically to liquid column hydrostatic instruments. ...