Definition of azulene
plural -s
1 a
: a liquid hydrocarbon C15H18 of intense blue color found in some essential oils (such as oil of cubebs) and in lignite tar
b
: any of various blue to violet or green hydrocarbons closely related chemically to this hydrocarbon and occurring naturally in essential oils or formed from various colorless naturally occurring sesquiterpenes
2
: a synthetic blue crystalline unsaturated bicyclic hydrocarbon C10H8 that resembles the isometric naphthalene in some properties but is more active chemically and that is the parent compound of the azulenes; cyclo-penta-cyclo-heptene
