The sound a dinosaur makes when it screeches, specifically a Velosoraptor, used as a substitute for the first name of Rove McManus.
More letters = More Enthusiasm.
Larry: "H-hey Janet, did you see RRAAUUURRGH last night?"
Janet: "No Larry, I'm not a fan of RAUURGH"
Mortimer: "Are you crazy, woman? I F-UCKING LOVE RRRRRAAAAAAUUUUUUURRRGHHH"