A Chad
A Chad is the spot between your balls and your butt. It's gross, it's smelly, and sometimes it's full of stuff you don't want to think about.
Chad: 'I was fingering that part, and it was full of crap.'
Chad: 'He had a stinky Chad, and it was gross.'
Chad: 'Don't measure your dick with the Chad, or you'll get crap on your tape.'