1The methyl anion CH₃ −, originally specifically in a compound with a metal atom. Later also: any compound that contains this anion or a substituted derivative of it.
2More fully "quinone methide". A quinone derivative with a methylene group in place of one of the oxygen atoms.
3A carbide whose anion is a single carbon atom (C4−), and which gives methane on hydrolysis.
Mid 19th century; earliest use found in Edward Frankland (1825–1899), chemist. From meth- + -ide.