Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or compound molecules made from a variety of atoms (e.g. carbon dioxide). A gas mixture would contain a variety of pure gases much like the air. What distinguishes a gas from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colorless gas invisible to the human observer. The interaction of gas particles in the presence of electric and gravitational fields are considered negligible, as indicated by the constant velocity vectors in the image.
The gaseous state of matter is found between the liquid and plasma states, the latter of which provides the upper temperature boundary for gases. Bounding the lower end of the temperature scale lie degenerative quantum gases which are gaining increasing attention. High-density atomic gases super cooled to incredibly low temperatures are classified by their statistical behavior as either a Bose gas or a Fermi gas. For a comprehensive listing of these exotic states of matter see list of states of matter.
Matter in a state intermediate between liquid and plasma that can be contained only if it is fully surrounded by a solid (or in a bubble of liquid) (or held together by gravitational pull); it can condense into a liquid, or can (rarely) become a solid directly.
“A lot of gas had escaped from the cylinder.”
A chemical element or compound in such a state.
“The atmosphere is made up of a number of different gases.”
A flammable gaseous hydrocarbon or hydrocarbon mixture (typically predominantly methane) used as a fuel, e.g. for cooking, heating, electricity generation or as a fuel in internal combustion engines in vehicles.
“Gas-fired power stations have largely replaced coal-burning ones.”
A hob on a gas cooker.
“She turned the gas on, put the potatoes on, then lit the oven.”
Methane or other waste gases trapped in one’s belly as a result of the digestive process.
“My tummy hurts so bad, I have gas.”
A humorous or entertaining event or person.
“He is such a gas!”
“The closer threw him nothing but gas.”
Arterial or venous blood gas.
Gasoline; a derivative of petroleum used as fuel.
To talk, chat.
To emit gas.
“The battery cell was gassing.”
To impregnate with gas.
“to gas lime with chlorine in the manufacture of bleaching powder”
To singe, as in a gas flame, so as to remove loose fibers.
“to gas thread”
To give a vehicle more fuel in order to accelerate it.
“The cops are coming. Gas it!”
To fill (a vehicle’s fuel tank) with fuel.
comical, zany; fun, amusing
“Mary’s new boyfriend is a gas man.”
“It was gas when the bird flew into the classroom.”
To draw in the breath suddenly, as if from a shock.
“The audience gasped as the magician disappeared.”
To breathe laboriously or convulsively.
“We were all gasping when we reached the summit.”
To speak in a breathless manner.
“The old man gasped his last few words.”
To pant with eagerness; to show vehement desire.
“I’m gasping for a cup of tea.”
A short, sudden intake of breath.
“The audience gave a gasp of astonishment”
: A draw or drag on a cigarette (or gasper).
“I’m popping out for a gasp.”
The sound of a gasp.
“Gasp! What will happen next?”
a substance or matter in a state in which it will expand freely to fill the whole of a container, having no fixed shape (unlike a solid) and no fixed volume (unlike a liquid)
“hot balls of gas that become stars”
a gaseous substance that cannot be liquefied by the application of pressure alone.
a flammable gas used as a fuel
“cooking is done by bottled gas”
a gaseous anaesthetic such as nitrous oxide, used in dentistry.
gas or vapour used as a poisonous agent in warfare
“gas was one of the most dreaded weapons of the war”
gas generated in the alimentary canal; flatulence.
an explosive mixture of firedamp with air.
short for gasoline
“we stopped for gas”
used in reference to power or the accelerator of a car
“I ordered my friend to step on the gas”
an entertaining or amusing person or situation
“the party would be a gas”
enjoyment, amusement, or fun
“it was great gas in the club last night”
kill or harm by exposure to gas
“my son was gassed at Verdun”
(of a storage battery or dry cell) give off gas
“the maintenance-free charger controls the input without inducing gassing”
talk excessively about trivial matters
“I thought you’d never stop gassing”
fill the tank of (a motor vehicle) with petrol
“after gassing up the car, he went into the restaurant”
very amusing or entertaining
“Ruthie, that’s gas—you’re a gem”