See also wOOt
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.