pepsin

UK: /ˈpɛpsɪn/ US: (pep′sin)

WordReference Random House Unabridged Dictionary of American English © 2025

pep•sin  (pep′sin), n. [Biochem.]

1. Biochemistry an enzyme, produced in the stomach, that in the presence of hydrochloric acid splits proteins into proteoses and peptones.
2. Biochemistry a commercial form of this substance, obtained from the stomachs of hogs, used as a digestive, as a ferment in the manufacture of cheese, etc.

Also, pep′sine. 

• Greek péps(is) digestion (pep-, base of péptein to digest + -sis -sis) + -in²
• 1835–45

Collins Concise English Dictionary © HarperCollins Publishers::

pepsin, pepsine / ˈpɛpsɪn/ noun

1. a proteolytic enzyme produced in the stomach in the inactive form pepsinogen, which, when activated by acid, splits proteins into peptones

Etymology: 19th Century: via German from Greek pepsis, from peptein to digest