When a veteran infantryman would meet another veteran, the question would be asked: "Are you a turtle?". To which the challenged veteran would have to either reply "You bet your sweet ass I am!" or have to buy the challenging veteran a drink.
or an inexperianced user
Can also be used as an adverb, which is a recently new development and is expected to catch on quickly
A Turtle thinks that his mystical stories and fabulous achivments will make him popular, but has absolutely no clue that nobody believes him... EVER.
Dude, he's a turtle don’t believe everything you hear.