A chemical reaction in which an ester is heated with an alkali (especially the alkaline hydrolysis of a fat or oil to make soap)

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Hydrolysis \Hy*drol"y*sis\, n. [Hydro-, 1 + -lysis.] (Chem.) A chemical process causing the splitting of a chemical bond by the addition of the elements of water. Where the bond which is split is not part of a ring structure, this process causes formation ...

Wiktionary Word definitions in Wiktionary
n. 1 (context chemistry English) The hydrolysis of an ester under basic conditions to form an alcohol and the salt of the acid. 2 The reaction of a metallic alkali (base) with a fat or oil to form soap.

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
1801, from French saponification , from saponifier , from Modern Latin saponificare , from sapon- "soap" (see soap (n.)) + -ficare , from Latin facere "to make, do" (see factitious ).

Wikipedia Word definitions in Wikipedia
Saponification is a process that produces soap , usually from fats and lye .

WordNet Word definitions in WordNet
n. a chemical reaction in which an ester is heated with an alkali (especially the alkaline hydrolysis of a fat or oil to make soap)