methylene

from WordNet (r) 3.0 (2006)

methylene
    n 1: the bivalent radical CH2 derived from methane [syn:
         {methylene group}, {methylene radical}, {methylene}]

from The Collaborative International Dictionary of English v.0.48

Methylene \Meth"yl*ene\, n. [F. m['e]thyl[`e]ne, from Gr. ? wine
   + ? wood; -- a word coined to correspond to the name wood
   spirit.] (Chem.)
   A divalent hydrocarbon radical, {-CH2-}, not known in the
   free state, but regarded as an essential residue and
   component of certain derivatives of methane; as, methylene
   bromide, {CH2Br2}; -- formerly called also {methene}.
   [1913 Webster]

   {Methylene blue} (Chem.), an artificial dyestuff consisting
      of a complex sulphur derivative of diphenyl amine; --
      called also {pure blue}.
      [1913 Webster]