An extremely overweight male. One who's moobs are larger then most women. A scary cat usually has problems breathing, often sounding like Darth Vader. A scary cat will often forget if he applied deodorant. Possibly sniffing his underarms in public or meetings. Finally, a scary cat could have a high pitch voice, like a little girl stuck in a man's body. The could easily be confused with the "We Shall Go To War" pirate in At World's End.
Did you just see that fat guy in the meeting? He is one scary cat.