Definition of gases:
(n) :
(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.
(n) :
(uncountable) A flammable gaseous hydrocarbon or hydrocarbon mixture used as a fuel, e.g. for cooking, heating, electricity generation or as a fuel in internal combustion engines in vehicles, especially natural gas.
(n) :
(uncountable, military) Poison gas.
(n) :
(countable, physical chemistry) A chemical element or compound in such a state.
(n) :
(countable) A hob on a gas cooker.
(n) :
(uncountable) Methane or other waste gases trapped in one's belly as a result of the digestive process; flatus.