A person who impedes the flow of traffic by staying in the left lane. This person is either driving slower than everybody on the road, driving the same speed as the person to their right, or simply driving 1 mph faster than the person to their right. In all cases, they are ignoring the responsibility that comes with driving in the "hammer lane".
Driver drives in left left despite seeing the long line of cars behind them but refuses to move over to the slow lane because it isn't safe to change lanes while talking on the cellphone. This driver is a Left Lane Loser.
A so-called grown-up who doesn't want to grow up (or at least act like an adult) and would instead prefer so-called "children's" stuff for entertainment, like cartoons, toys, comic books, Disney movies, etc. He or she also enjoys colorful "kiddie" snacks like breakfast cereal and Spaghetti-O's and dresses like a teenager or perhaps younger. May or may not be great parents as well as being able to take on adult responsibilities. Not necessarily too immature at least in the public. Not to to be confused with geeks or nerds either, of course!
Also known as "Peter Pan", "young at heart", and "kid at heart".
I'm almost 35 and I love Neopets, Archie comics, children's books, etc. So this makes me a kidult, heh.