Noise made by brass players in their earlier years, particularly the trombone. May be used to imitate bad playing, along with words like "frack" and "fwah". Usually occurs at the ends of phrases when the player runs out of air.
When your girlfriend bursts into tears over the accommodations you've selected for your romantic getaway, you've booked a boo hoo hotel.
"CeCe saw the stains on the carpet and sheets and felt herself tear up. We both understood without a word. I'd picked a boo hoo hotel again, and no one was ever going to get lucky in that dump."