n. [ F. méthylène, from Gr. &unr_; wine + &unr_; 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 ]

n. a drug designed to have the effects of amphetamines but to avoid the drug laws, but now a controlled substance. Called also MDMA.
Syn. -- MDMA, Adam, ecstasy. [ WordNet 1.5 ]

n. [ Oxy- (a) + methylene. ] (Chem.) Formic aldehyde, regarded as a methylene derivative. [ 1913 Webster ]

n. [ Penta- + methylene. ] (Chem.) A hypothetical hydrocarbon, C5H10, metameric with the amylenes, and the nucleus of a large number of derivatives; -- so named because regarded as composed of five methylene residues. Cf. Trimethylene, and Tetramethylene. [ 1913 Webster ]

n. [ Tetra- + methylene. ] (Chem.) (a) A hypothetical hydrocarbon, C4H8, analogous to trimethylene, and regarded as the base of well-known series or derivatives. (b) Sometimes, an isomeric radical used to designate certain compounds which are really related to butylene. [ 1913 Webster ]

n. (Chem.) A gaseous hydrocarbon, C3H6, isomeric with propylene and obtained from it indirectly. It is the base of a series of compounds analogous to the aromatic hydrocarbons. [ 1913 Webster ]