Source : Webster's Revised Unabridged Dictionary (1913)

Propylene \Pro"pyl*ene\, n. [Cf. F. propyl[`e]ne.] (Chem.)
   A colorless gaseous hydrocarbon ({C3H6}) of the ethylene
   series, having a garlic odor. It occurs in coal gas, and is
   produced artificially in various ways. Called also {propene}.

Trimethylene \Tri*meth"yl*ene\, n. (Chem.)
   A gaseous hydrocarbon, {C3H6}, isomeric with propylene and
   obtained from it indirectly. It is the base of a series of
   compounds analogous to the aromatic hydrocarbons.