See also: demethylation French Etymology From dé- + méthylation or from déméthyler + -ation. Pronunciation Audio:(file) Noun déméthylation f (plural déméthylations) (organic chemistry) demethylation Further reading “déméthylation”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012.Wikiwand - on Seamless Wikipedia browsing. On steroids.