When you show impudence, you lack shame about your rude behavior. Examples of impudence? Not tipping the waiter, sticking your tongue out, tripping your grandmother — you get the picture.
The noun impudence is derived from the Latin impudentia, "shamelessness." Being rude is a main trait of impudence; another is doing something you're not supposed to do — usually with an attitude that shows you don't care. When you are acting with impudence, you are usually overstepping your boundaries — like a kid who challenges his parents and can't accept "Because I said so!" as a reason for discipline.