pep·​sin | \ ˈpep-sən How to pronounce pepsin (audio) \

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 In 2012, a lab study showed that water with a pH of 8.8 neutralized pepsin, the enzyme that causes damage to the esophagus in people with acid reflux. SELF, "What Even Is Alkaline Water and Is It Really Better Than Regular Water?," 6 Sep. 2018 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

Keep scrolling for more

Learn More about pepsin

Time Traveler for pepsin

Time Traveler

The first known use of pepsin was circa 1844

See more words from the same year

Statistics for pepsin

Cite this Entry

“Pepsin.” Dictionary, Merriam-Webster, Accessed 14 Aug. 2020.

Keep scrolling for more

More Definitions for pepsin


pep·​sin | \ ˈpep-sən How to pronounce pepsin (audio) \

Kids Definition of pepsin

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


pep·​sin | \ ˈpep-sən How to pronounce pepsin (audio) \

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

More from Merriam-Webster on pepsin Encyclopedia article about pepsin

Comments on pepsin

What made you want to look up pepsin? Please tell us where you read or heard it (including the quote, if possible).


Test Your Vocabulary

Name That Thing: Animal Edition

  • alt 5a023732e6f75
  • Name that animal:
Spell It

Can you spell these 10 commonly misspelled words?

Dictionary Devil

Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!