"w00t" was originally an trunicated expression common among players of Dungeons and Dragons tabletop role-playing game for "Wow, loot!" Thus the term passed into the net-culture where it thrived in video game communities and lost its original meaning and is used simply as a term of excitement.
"woot! i r teh flagmastar!" (Think Tribes)
"Woot, I pwnzed this dude's boxen!'
1) An interjection similar to "YAYE!" or "Woohoo!" used to express joy or excitement, usually about some kind of accomplishment. Primarily used by gamers, spreading rapidly to anyone who chats online
Gaming origins: We Owned the Other Team
or Wonderful Loot (Everquest gaming slang)
2) To express agreement
3) As an acronym, can mean Waste of Our Time or Way Out of Topic (online forums) Less common.
2)Robyn: Eric is such a tool. Let's put packing peanuts in his desk.
It originated from back in the days of MUD games, after killing an opponent loot was a rare find, so if someone found loot they would say "wow loot!". This evolved into "woot" for short which further evolved to simply be a general exclamation of excitement.
Bob: I just killed a monster! woot!
Bob: Something good just happened! w00t!