(also 'Dropping') To 'drop' is to leave a multiplayer game before it has ended. The drop can be caused by technical problems (ex. a person's computer loses it's internet connection, or lags so badly the player's screen becomes frozen and they need to restart Myth) or it can be the result of the player deciding to leave the game.
Dropping often has a rather negative connotation because back when Bungie.net had hordes of people playing Myth on their game server, and competition for the highest rank was fierce, 'dropping' was often employed by lame players who dropped out of games rather suffer a defeat and the resulting loss in rank.
On mariusnet there is an automatic drop penalty against people who drop out of games in ranked rooms. You will lose points everytime you drop.