21 CFR 335.3 - Definitions.
As used in this part:
(b)Diarrhea. A condition characterized by increased frequency of loose, watery stools (three or more daily) during a limited period (24 to 48 hours), usually with no identifiable cause.
(c)Travelers' diarrhea. A subset of diarrhea occurring in travelers that is most commonly caused by an infectious agent.