The DICT Development Group

  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]

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