In the context of real life someone who spends periods of time in an area, therefore you may
even consider your home a campsite.
In the context of
video games, mainly first person shooters camping varies, for example in a game like Battlefield
3 or Team fortress 2, taking cover to guard an objective or
flag or other such position may sometimes be necessary, however in a game like Call Of Duty Modern Warfare 3 it is considered- with
good reason, an illegitimate tactic, mainly because if it's an objective game mode. The camper may leave the objective for the purpose of only gaining kills for himself, or it may occur when they wish to maintain a K/D. With the killspeed of
guns in call of duty it only makes sense to frown upon this, since the maps are so tiny in call of duty there is no sniping either.