A fanny blaster is an individual with the ability to blast their fanny; known to scientists as the phenomenon of ejactualating large amounts of carbon dioxide into the atmosphere, contributing to global warming considerably.
Also used metephorically to describe someone of a gasey nature, i.e talks a load of shite.
policeman: we have a situation here, can't breathe
emergency services: calm down, whats the assesement?
policeman: we've got us a fanny blaster!
"greg, you complete and utter fanny blaster"