Ethylidene \E*thyl"i*dene\ (Chem.)
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.
[1913 Webster]
