noun

• (organic chemistry, countable) Any organic compound having one or more carbon–carbon triple bonds; an alkyne.
• (organic chemistry, uncountable) Ethyne; the simplest alkyne, a hydrocarbon of formula HC≡CH. It is a colourless, odourless, extremely flammable, explosive gas, formerly used as an illuminating gas, but now used in welding and metallurgy.
• A lamp powered by acetylene, particularly a motor vehicle headlight.