Flap burp

When you go down on a lass, spread her legs to open the heavenly gates, as you go down on her you do a loud burp right between the flaps. ( excessive amounts of either alcohol or gas-inducing drinks help with vibrations)

(Dan) Do you remember that 'Shiela' from the bar last night Shane?
(Shane) yeah the one with the fat arse?
(Dan) yeah mate that's the one, well I took her home and after all that beer.......I had to give her the good ol' flap burp!