GNU Collaborative International Dictionary of English

Found one definition

1.       
   Methylene , n. [F. méthylène, 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