Live Action Role Play (n)
Verb form: To LARP, LARPing, LARPed, etc.
LARPs are a category of game in which players create characters and, acting as those characters, interact with other players and Storytellers/Game Masters to complete some sort of challenge, quest, or adventure. LARPing traditionally has its roots in so-called "table top" games like Dungeons and Dragons or White Wolf's Vampire the Masquerade, however in table top games, the game mechanics are controlled by dice. In LARPing, game mechanics are usually controlled by rock-paper-scissors.
Although some forms of LARPs do include foam weapons (known as "Boffer weapons") and medieval/fantasy costuming, others take place in the real world with current clothes and can be played in public spaces so long as players have an identifying object such as a red button or other signifier to tell other players who is involved in the game. These games generally do not include actual weapons of any sort, foam or otherwise, and players wishing to use a weapon against another character must describe what they are doing and then play rock-paper-scissors to determine if they are successful.
Vampire the Masquerade is one of the more successful LARPs out there, having several groups throughout the United States. Large numbers of LARPers are therefore often walked past by unsuspecting passerby who think they've just seen a bunch of loitering goths. Although they are not wrong, they have also witnessed LARPing.
I was LARPing last night and my Toreador character became Primogen of her Clan. Then I was attacked by a Nosferatu and lost Rock-Paper-Scissors, so now I'm waiting for the Storyteller to tell me if I've been unstaked yet.