P.U. Definition

Used to express disgust, revulsion, etc. in response to an offensive odor or to anything felt to be unpleasant or offensive.
Webster's New World

(euphemistic) An interjection in response to smelling an unpleasant scent; an exaggerated pronunciation of pew.

What is that awful smell? P U!

Origin of P.U.

  • Possibly from Spanish fu, an interjection indicating disgust, or from French puer (“to stink”)

    From Wiktionary