The act of fellatio performed on a man who is having a bowl movement on the toilet. iow, giving head to a guy while he's taking a huge dump.
Referenced briefly in the american pie: beta house movie, wherein a test to join a fraternity includes the requirement of receiving said carnal pleasure.
could possibly refer to the act performed on a woman, but the logistics are much more complicated
"Yo, your mom gave me some grundleingus last night."
Fogey/fogy /fougi/ sl. (early 18C+, orig. Scot) old-fashioned, stuck-in-the mud.
Person with old fashioned ideas which he is unwilling to change: Come to the disco and stop being such an old fogey!
You think me an old fogeyand an old tory, his thoughtful voice said. I saw three generations since O’Connel’s time. I remember the famine. Do you know that the orange lodges agitated for repeal of the union twenty years before O’Connel did or before the prelates of your communion denounced him as a demagogue? You fenians forget some things. (James Joyce, Ulysses. Penguin Books,1992. p. 38)