When a woman is preforming the art of "salad tossing" and one's self relieves himself by releasing an excrament of his own natural gas (farts) into her mouth. Usually preforming the London Fog Horn will leave the recipiant in an irate state of mind and has been know to lead to a violent reaction.
I was watching this porno when this dude gave this bitch the "London Fog Horn" and man did she get pissed off! Man that shit was funny!
by Billy Bingham November 09, 2006
During fellatio the recipiant jabs the donor's chest directly between the lungs. The donor then reacts by expelling a prolonged deep tone, comparable to that of a fog horn.
Last night my boyfriend gave me a London Fog Horn. It woke my grandmother up.
by Garyland May 29, 2008