Calling Four Christmases a lump of coal demeans that fossil fuel’s many uses. Besides, if estimates hold, coal’s noxious chemical aftereffects could be gone by 2025. Vince Vaughn and Reese Witherspoon can only hope this dissipates by then.

Four Christmases is a rancid, shrill, toothless, senseless disaster that furiously scrapes at the barrel’s bottom even more than holiday tripe like Deck the Halls. Vaughn and Witherspoon have no spark as yuppies unwittingly forced to spend holidays with their estranged kin.

“Mistletoe” is their safe word to escape familial sadomasochism. Those dragged to this joyless mess won’t find themselves so lucky. Rooting for that duo in this romantic comedy is like being asked to cheer on the joyless relationship of Todd and Margo in National Lampoon’s Christmas Vacation.

Pathetically mimicking Spider-Man 3, where children commented on “cool” action, Four Christmases has shots of people laughing at Vaughn and Witherspoon. The comedy isn’t contagious, but Four Christmases is, like a lingering virus, filled with nasty, violent side effects.

Vaughn and Witherspoon are Brad and Kate, a San Francisco couple unmarried for fear of turning out like their own parents — separated and estranged. On his side, it’s Robert Duvall and Sissy Spacek. On hers, Jon Voight and Mary Steenburgen.

Each Christmas, Brad and Kate fib about flying away for international charity work. Instead, these self-centered twits fly to tropical paradises far from the familial vitriol. Vaughn gets his usual smarmy, snake-oil chuckles in these shyster scenes.

When a flight to Fiji is canceled due to fog — and Brad & Kate end up on the TV news because of it — their families phone them to come visit. So begins a quadruple shot of misery for them, and audiences expecting a quality shot of Christmas comedy.

At Brad’s dad’s white-trash paradise, his ultimate-fighter brothers (Jon Favreau and Tim McGraw) beat him senselessly, and humorlessly. Visiting the Pottery Barn-perfect home of Kate’s mother, Kate is beset by maternal instincts, a breastfeeding sister (Kristin Chenoweth), a church skit gone wrong and 8-year-olds executing perfect dropkicks. Seriously, it’s like a wrestling comedy in the guise of Christmas.

Brad’s mother is sleeping with his one-time best friend, and board games turn sour. With a dementedly successful round of “Taboo,” Favreau and Katy Mixon, as his pregnant wife, have the film’s lone laugh-out-loud bit not spoiled by the trailer.

Lastly, Brad and Kate confront their iffy future at her father’s palatial palace. Voight’s home looks more like Connecticut than California, and his big dramatic scene feels like a plea for Angelina to let him see Knox and Vivienne. The movie’s emotional moments carry all the subtlety of a drill press to the temple.

It’s easy to see what director Seth Gordon saw, aside from a star vehicle, in Four Christmases. It wants to go for the same bleakly funny morass of American expectations as The King of Kong: A Fistful of Quarters — his flawless video-game documentary.

But unlike Step Brothers, which successfully mocked measurements of male success, Four Christmases is toothless. And Gordon seems visibly lost – “zany” zooms, lighting that Fox sitcoms wouldn’t employ, cheap sight gags and one of the decade’s most rambling, and ridiculous, romantic-comedy reconciliations.

If it’s comedic cheer through Christmas jeer you’re looking for, re-watch The Ref, Bad Santa or even the unfairly maligned Surviving Christmas. Forget these fictional fractured families with which Vaughn and Witherspoon must contend. Four Christmases creates its own holiday hell from which to escape.