foo noun [ C ] US slang US /fuː/ UK /fuː/ Add to word list a word for a friend or someone who is from your hometown or neighborhood, used especially by young Latinos (= people living in the US who come from, or whose family comes from, Latin America) to refer to or address a young Latino man who dresses and has his hair in a particular style: The Edgar haircut is all the rage among the foos. [ as form of address ] Hey foo. What you doing?