Acetylene

Etymology
From acetyl: + -ene:.

Noun

 * 1)  Any organic compound having one or more carbon–carbon triple bonds; an alkyne.
 * 2)  Ethyne; the simplest alkyne, a hydrocarbon of formula HC≡CH. It is a colourless gas, with a peculiar, unpleasant odour, formerly used as an illuminating gas, but now used in welding or metallurgy.

Synonyms

 * ethyne