In ancient Greece: The sin of thinking you are above the gods or forgetting to give them credit when they have helped you. Of course they don't tell you when they help you, you are just supposed to know. Committing hubris ALWAYS leads to nemesis, the gods' punishment.
Oedipus: Yes! I have rid this country of evil. All by myself! *hubris*
Athena: No, damn it, I helped you! Respect me! Oh well, I'll just kill you then. *nemesis*
An adjective used to describe an action of grotesquely unnecessary talent, finesse, or pride that ends in resounding (though somewhat satisfying) failure.
In gaming - when players makes a hubris effort that, while lookingawesome, ends in their death or failure
E.g. Thomas Tomstall passed his driving test making a point out of it by jingling his keys and comparing his driving skills to the size of his penis. Later that day young Thomas was driving down a country lane at 90mph when low and behold he got air in his car and flipped over a ravine.
The next day when his class mates found out about Thomas's fate all that could be said was "LOL! HUBRIS!"