Highest-ranked player to lose in the final round of qualifying, but still gain acceptance into the main draw of a tournament due to a main draw player's withdrawal. In Grand Slam events, one of the four highest-ranked losers in the final qualifying round is randomly picked as the lucky loser. Found on http://en.wikipedia.org/wiki/Glossary_of_tennis_terms
A lucky loser is a sports player who loses a match in the qualifying round of a knockout tournament, but who then enters the main draw when another player withdraws after the tournament has started because of illness, injury or other reason. The lucky loser then enters the main draw, normally in place of the withdrawn player. This can only happen ... Found on http://en.wikipedia.org/wiki/Lucky_loser