Usually some limpdick, no-skill loser-scrub who feels the need to intentionally lag the game in order to win. Most commonly used in fighting games and FPS games.
He's definitely a lag switcher, I played against him online and when I was about to beat him and then the game suddenly started lagging when I tried to block his ultimate, he won and left without saying anything.
To mess something up royally, also used by the character Tito from the Nickelodeon show: Rocket Power.
Person 1: Where's my dog?
Person 2: I really got some sand in the potato salad, he escaped and is now loose.
Person 1: We better go looking for it.