Based on the 11 hour 5 min match at Wimbledon featuring Nicholas Mahut (FRA) and John Isner (USA) where they played 138 games in the fifth set alone and where most records were completely shattered.
It refers to anything an event or oddity that will almost positively never happen again.
The strange disappearance of an entire civilized city in Mexico was a once a marathon match
by akararules June 24, 2010
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