A waddy is a
piece of shit with corn (or peas) in it.
Sometimes when you don't chew peas or corn enough, they become viewable when you do a shit. When you call someone a waddy, you are calling them the above
description. A waddy looks very discusting and sometimes dogs do them too. So when you eat corn and notice sweetcorn
in your shit, you just did a waddy.
person 1: "Oh man I just did a big waddy.."
Person 2: "oh yuck dude, was there much corn?"
OR
"your'e a big fat waddy"
"your'e a
piece of shit with corn in it, you waddy!"