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 marathonmatch
An exceptionally long episode of masturbation fits. These episodes are usually brought on by sexual deprivation and bordom; however, and I'm not making this up, they have been used a means of fundraising for sexual related causes such as safe sex. A masturbation marathon is a strenuous event that requires disciplined training and preparation. There are several related subcatagories such as time, ejaculation distance, and most orgasms for both male and female competitors (I'm totally serious - google it).
Something of a daily occurance, NCIS is a great show and it seams its so great that they have "Marathon's" almost everyday. Do not get sucked in as these last for 12-24 hours and you will get nothing done.
Person 1: I'm going to work on my project *walks into TV room* EWWW!!! NCIS Marathon! *Two hours later*: Shit I got nothing done!
another term for a station wagon, mini-van, or any other kind of vehicle that is targeted at the "family" demographic(also M.A.V.)
"Tactical advantages aside, the M.A.V. is top of the line for the holy warrior troop transport manufactured by the Church of Latter Day Saints Military Industrial Complex. Also great for family trips...to heathen lands."
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.