From SA Mafia Wiki
EXLO, or Execute or Lose (commonly lylo, for lynch or lose), is a final stage of the game, in which players must execute scum or else they will lose. EXLO occurs when the number of remaining townies in the game is one (or sometimes even two) more than the number of remaining scum. If the players execute wrongly, the scum will take over the majority of the town with their nightkill and win the game. During EXLO, players must be careful with their votes, as the remaining scum can easily bandwagon onto an errant vote and win the game.
While rare, it is possible for town to be unable to win in a EXLO-like scenario, especially if multiple killing roles are involved. For instance: if there are two townies, a mafioso, and a Serial Killer.