The act of passing gastric wind directly from one anal cavity to another which is subsequently re-released by the receiver.
The 'fartee' bends over and parts his arsecheeks with his hands revealing a gaping anus. The 'farter' then positions his anus against that of the fartee and breaks wind directly into the fartee's anal cavity. The fartee then clenches his anus shut thus trapping the wind of the farter. In his own time he then releases the fart as if it were his own. The fartee has become the farter. This is a back door blowback.
Hey Dude, I gave that bird a stonking back doorblowback the other night, it fucking reeked!
Microscopic, particulate matter expelled from one's anus during flatuent activity, usually confined to one's underwear if such garments are in fact being worn, though its infinitesemal size can still disperse into the surrounding airregardless of the presence of protective garments thus landing on your peanut butter and jelly sandwich.
Johnnyripped a huge fart when his girlfriend, Carmen, was talking on the phone and she did not realize that his fecal blowback landed in her Cesar salad.
To hold a marijuana joint in ones mouth between the lips with the hot end in the mouth while blowing smoke out of the hole at the other end into someone else's mouth, so as to get a big 'hit'
When you and your partner are num numing eachothers no-no parts at the same time, and one partner farts (accidentally or on purpose) in the other partners face, mouth or nose, thats a blowback 69. Blow blowback fart face fart in face 69