allene
noun
al·lene
ˈaˌlēn
plural -s
1
: a gaseous hydrocarbon CH2=C=CH2
called also propadiene, sym-allylene
2
: a diolefin with its two double bonds in adjacent positions
Word History
Etymology
International Scientific Vocabulary, contraction of allylene
First Known Use
1875, in the meaning defined at sense 1