Gas \gas\ (gâs), n.; pl. gases (-êz). [Invented by the chemist Van Helmont of Brussels, who died in 1644.]

1. An aëriform fluid; -- a term used at first by chemists as synonymous with air, but since restricted to fluids supposed to be permanently elastic, as oxygen, hydrogen, etc., in distinction from vapors, as steam, which become liquid on a reduction of temperature. In present usage, since all of the supposed permanent gases have been liquified by cold and pressure, the term has resumed nearly its original signification, and is applied to any substance in the elastic or aëriform state
2. (Popular Usage) (a) A complex mixture of gases, of which the most important constituents are marsh gas, olefiant gas, and hydrogen, artificially produced by the destructive distillation of gas coal, or sometimes of peat, wood, oil, resin, etc. It gives a brilliant light when burned, and is the common gas used for illuminating purposes (b) Laughing gas (c) Any irrespirable aëriform fluid
3. Gasoline [Colloq.]
4. The state of matter distinguished from the solid and liquid states by: relatively low density and viscosity; relatively great expansion and contraction with changes in pressure and temperature; the ability to diffuse readily; and the spontaneous tendency to become distributed uniformly throughout any container
5. A fluid in the gaseous state having neither independent shape nor volume and being able to expand indefinitely
6. A volatile flammable mixture of hydrocarbons (hexane and heptane and octane etc.) derived from petroleum; used mainly as a fuel in internal-combustion engines [syn: gasoline, gasolene, petrol]
7. A state of excessive gas in the alimentary canal [syn: flatulence, flatulency]
8. A pedal that controls the throttle valve; "he stepped on the gas" [syn: accelerator, accelerator pedal, gas pedal, throttle, gun]
9. A fossil fuel in the gaseous state; used for cooking and heating homes [syn: natural gas]

Gas \gas\, v. t. [imp. & p. p. gassed; p. pr. & vb. n gassing.]

1. (Textiles) To singe, as in a gas flame, so as to remove loose fibers; as, to gas thread
2. To impregnate with gas; as, to gas lime with chlorine in the manufacture of bleaching powder
3. attack with gas; subject to gas fumes; "the despot gassed the rebellious tribes"
4. show off [syn: boast, tout, swash, brag, blow, bluster, vaunt, gasconade]