What is "acenaphthene"

n. (context organic compound English) A hydrocarbon, found in coal tar, derived from naphthalene by the addition of a short aliphatic bridge.

Acenaphthene is a polycyclic aromatic hydrocarbon (PAH) consisting of naphthalene with an ethylene bridge connecting positions 1 and 8. It is a colourless solid. Coal tar consists of about 0.3% of this compound.