A videogame is rendered unwinnable when it allows a player to make a mistake that can not be corrected. The result is a game that can not be won. Worse, the text adventures and graphic adventures that such a situation arose in rarely bothered to notify the player that they would never succeed in their quest, leaving them to trudge around the game world forever like the walking dead.
My favorite instance of this is in King’s Quest V. Early in the game, King Graham has the opportunity to buy a pie from a bakery. He only has enough money for one pie and, unbeknownst to him, the pie is needed for a situation later in the game, so if he eats the fresh, delicious looking treat like a normal human being, the game becomes unwinnable. If King Graham wisely but illogically keeps the pie in his travel pack, he later comes across a vulture starving in the desert. This poor creature is the reason divine providence delivered that pie into Graham’s possession, surely? Alas, no. If you feed the wretched vulture the pie, the game again becomes unwinnable. Why? Because later, King Graham will encounter a fearsome yeti on a cliff in a high, snowy mountain and the only way to defeat the creature is to hit it in the face with the pie, knocking it over the edge to its doom.
The unwinnable trap distills everything that is frustrating, mean, backwards and counter intuitive about those videogames.
What better name for a videogame website?