气体 — meaning in English

qì tǐ

English meaning

gas noun A state of matter, like air, that has no fixed shape or volume and spreads to fill its container.

气体 is used for these senses in English:

gas (uncountable, physical chemistry) Matter in an intermediate state 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 by deposition.
gas (countable, physical chemistry) A chemical element or compound in such a state.
welly (uncountable, informal) Force on a pedal or increase to any fuel or power for an engine or motor.

noun A state of matter, like air, that has no fixed shape or volume and spreads to fill its container.
noun A fuel, especially natural gas used for heating and cooking, or (US, informal) petrol for a vehicle.
noun Air trapped in the stomach or intestines; flatulence.
verb To attack or kill using poisonous gas.
verb (informal, US) To fill a vehicle's tank with fuel.