Not only that, it’s the "word of the year". (Last year’s "word of the year" was Stephen Colbert’s "truthiness").
It’s actually spelled with two zeroes instead of two os’, as in "w00t".
"Woot" is an exclamation of joy or triumph, usually accompanied by a waving of the fist in the air. Although the article doesn’t mention it, I believe it originally derives from the audience reactions during the 1980’s Arsenio Hall show.