The definition: A person who actually pays to crawl through, be encrusted in and sometimes flip into mud. A tough mudder is a person who does it over 12-and-a-half miles of muddy track, through wire electrified to 10,000 volts and what seem like medieval torture devices with names like "Arctic Enema."
Welcome to the Tough Mudder. Don't call it a race, "it's a challenge," admonish the organizers, who are bringing their British-special-forces-designed (read painful) courses with their 29 obstacles (walls, 15-foot planks, ice baths, nightmare monkey bars, greased halfpipes, electrified army crawls, etc.).
I attended one of 35 tough mudder events being held this year. It's one of the fastest growing businesses in America, going from 50,000 participants in 2010 to a projected half million in 2012.
It's competitive, to an extent. The goal, said a wise-cracking emcee psyching up the crowd of 6,000 before our start time, is to do your best, but also to help your fellow mudder.
"If you find someone face down in the dirt, they are no longer enjoying the course -- help them," he said.
It was among those hundreds milling around, stretching in their compression shorts, head bands -- many were bare-chested -- that I found perhaps the toughest mudder about to start the race.
A former Marine, Ben Lunak was standing with a group of wounded warriors at the aptly named Mesa Proving Grounds in Mesa, Ariz., where 6,000 pain-craving lunatics gathered for the Tough Mudder.
Lunak's Humvee was blown up near Ramadi, Iraq, in 2005. When he went to in Germany a few days later he looked down, surprised that his leg was still attached. And then he asked for it to be amputated.
"If they left it," he told me, "it would just be a bum leg and I would be walking around with a cane, and that's pretty much worthless. I just wanted to get out of the hospital, and I said, 'Why wouldn't you amputate it? What are we waiting for?'"
Lunak nearly ascended Mount Kilimanjaro last year, and now he was attempting this -- something the organizers have proudly branded, "probably the toughest race on the planet."
I asked another wounded warrior what attracts them to something like this. One would think it's just more pain for people who've been through so much already.
His answer: "It is! It's great pain! There's only a few wounded warriors here and we've been through this before and we'll do it time and time again, and we're just gluttons for pain. ... Gluttons for pain, we love it."
These were the people I'd be running with. It was going to be a long day.
Every tough mudder begins with a preemptive pledge to suck it up. I do not whine. Kids whine. I help my fellow mudders complete the course, and I overcome all my fears.
The race began. It seemed easy enough, a few mud crawls beneath barbed wire, a couple of obstacles like hay bales and giant ruts. And then came the official Tough Mudder reminder that this was no jog in the park: the Arctic Enema.
"It's a dumpster filled with ice water, it's absolutely freezing. It's the mother of all ice cream headaches," said Alex Paternson, the Mudder's marketing chief.
He's one of the people who devises names like Arctic Enema, Devils's Beard, Shocks on the Rocks and Funky Monkey.
He's also a Harvard graduate with a law degree. Ergo, the other part of his job: ensuring that the sadistic, surprisingly legal obstacles don't get the fledgling company sued.