A griefer is considered to be someone who plays an online game with the sole purpose of causing grief to the other players, normally through harassment; this is normally referred to as “griefing”. Originally used in baseball as a derogatory term by away teams talking about the home side, it began being used to refer to gamers by around the year 2000.

Recently, the term has been used (such as in the More4 News video clip available from this page) to describe protesters in the online world of Second Life, such as the SLLA (Second Life Liberation Army).