An exclamation or interjection indicating that one has smelled a foul odor or stink. Properly pronounced with one's nose either wrinkled in disgust or pinched with the fingers to block the stench. Sometimes written "Pee-yew" or "P.U."

"Oh my God, the dog got sprayed by a skunk. PU!"

This expression may be related to "phooey", "phew", or the Yiddish expression of disgust, "feh". If so, it may share etymology with the ubiquitous "foo".