1. Short for Loss Of Signal, LOS is an indicator on a networking device to indicate that a network signal or connection has been lost. If a LOS is encountered, the cable connected to the network device is bad, has no connection on the other end, network is improperly configured, or the network device itself is bad.
2. Line of Sight (LoS) means a character or other player is not in visible sight of another character or player. In some games, this prevents a player from selecting a target or another player, preventing them from performing any number of actions to help or harm the other player. Walls, hills, stairs, and trees are common objects that cause result in not being in Line of Sight of another player. How a game is programmed can determine what objects can cause Line of Sight issues.