| ̷ ̷ ̷ ̷ at cyclo- + noun
( -s )
Etymology: International Scientific Vocabulary cycl- + pentadiene (from pent- + di- + -ene )
: a colorless liquid unsaturated cyclic hydrocarbon C 5 H 6 that is obtained by distillation of coal tar, that polymerizes to its stable dimer on standing, and is used in making plastics and insecticides