pep·​sin | \ˈpep-sən \

Definition of pepsin 

1 : a protease of the stomach that breaks down most proteins to polypeptides

2 : a preparation containing pepsin that is obtained from the stomach especially of the hog and is used especially as a digestive aid

Examples of pepsin in a Sentence

Recent Examples on the Web

That’s because plant protein is digested mostly in the intestines, while animal protein is digested in the stomach—which is also the point of production for pepsin. Alice Park, Time, "Acid Reflux May Respond Better To Diet Than Drugs," 7 Sep. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'pepsin.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of pepsin

circa 1844, in the meaning defined at sense 1

History and Etymology for pepsin

German, from Greek pepsis digestion, from pessein

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Time Traveler for pepsin

The first known use of pepsin was circa 1844

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More Definitions for pepsin


pep·​sin | \ˈpep-sən \

Kids Definition of pepsin

: an enzyme that starts the digestion of proteins in the stomach


pep·​sin | \ˈpep-sən \

Medical Definition of pepsin 

1 : a crystallizable protease that in an acid medium digests most proteins to polypeptides (as by dissolving coagulated egg albumin or causing casein to precipitate from skim milk), that is secreted by glands in the mucous membrane of the stomach of higher animals, and that in combination with dilute hydrochloric acid is the chief active principle of gastric juice

2 : a preparation containing pepsin obtained as a powder or scales from the stomach especially of the hog and used especially as a digestant

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to clear from alleged fault or guilt

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