Octogenarian
A person who is old enough to know that life is a series of bad decisions and still makes all of them, especially the ones involving food and swear words.
My grandpa is an octogenarian and still makes all the worst decisions involving food and swear words.
My neighbor is an octogenarian and still eats ice cream for dinner and cusses at the mailman.
My uncle is an octogenarian and still thinks he's the best at everything, even though he's wrong.