Acronym for "Massively Multiplayer Online First Person Shooter".
Most support a large number of players in 1 server.
See also pwned
Some examples are: Planetside, World War II Online and Battlefield 1942. Many have a monthly subscription cost to pay for server access.
Similar to MMORPG
's, these games differ only in that you usually can see ahead in First Person and can fire some sort of projectile weapon, thus "killing" your opponent.