Ethylidene
Pronunciation : E*thyl"i*dene. (Chem.)
Definition : Defn: An unsymmetrical, divalent, hydrocarbon radical, C2H4 metameric with ethylene but written thus, CH3.CH to distinguish it from the symmetrical ethylene, CH2.CH2. Its compounds are derived from aldehyde. Formerly called also ethidene.
Source : Webster's Unabridged Dictionary, 1913