A nasty yet entertaining trick played by men on women (or other men depending on how you are).
Committed in the closing moments of a blowjob, It is the act of grabbing the recievers head and jamming it down on your dick as you cum, thus making them choke/gag, re-routing your cum out through their nose running out of both nostrils. Number 11.
A useful word, it can be used to point out a bum on the street bathing in his/her own mess or any terribly ugly person you have unfortunately come across.
Think of the ugliness of a bog and mix it with the dirtiness of a rat. And you have something very disgusting.
"Bloody hell, look at the face on that one!"
"Whoa! What a bograt!"