Stay clear of anyone possessing effrontery. (And if that person is YOU, then learn some manners! Tip: You’ll get farther in life if you do.) But back to the definition… Effrontery boils down to presumptuousness. Being overbearing and shamelessly bold. In a bad way. Not the kind of person you want to be hanging out with day in and day out.
Example: As Jack aged, his effrontery became legend. Since contractors hated him, design firms feared him, and lenders saw him as an unpredictable risk, he was having a harder and harder time getting his retail development projects off the ground.