1. Usually used in MOORPG's to describe an event where a high level NPC or monster kills your 10,000 hit point character in one fatal swoop.
2. Can also be used to describe an event where serious pwnage is credited.
1.My decked out Pally got One Shotted by Onyxia.
2.The snowboarding spill was so epic that dude got One Shotted to the top.