Its methods are unorthodox, ranging from targeted use of superglue to hijacking Twitter-based PR campaigns, and its rapidly growing support base spanning schoolchildren and pensioners has no official leadership.
But one thing about UK Uncut is certain: it is fast becoming one of Britain's most effective and unpredictable protest movements.
Started in the autumn by 12 activists in a north London pub discussing the issue of corporate tax avoidance, the campaign against public spending cuts will today stage demonstrations on high streets in more than 50 towns, many of them involving direct action to close the stores of some of the country's biggest retailers.
Vodafone and retail billionaire Sir Philip Green's Arcadia Group, two of the prime targets for the group, yesterday refused to discuss their plans for additional security at their shops to thwart sit-in protests at locations including London's Oxford Street on one of the busiest shopping days of the year.
Retailers are increasingly rattled by the success of the amorphous campaign. Vodafone described the protests as "baseless" but UK Uncut claims that the Treasury loses £25bn a year from tax avoidance by British companies.
The epidemic of students and grandmothers lying on pavements to bar access to global brands is just the latest example of the way in which Twitter and other social media websites are being used to mobilise loose coalitions of ordinary but angry citizens.
Hacking group Anonymous this week threatened to attack British government websites using "zombie" machines donated by thousands of users as part of its campaign against companies withdrawing support services for the WikiLeaks website.
UK Uncut, which has more than 30,000 followers on Twitter, has tripled the number of towns where it is demonstrating from 17 in October to today's total of 53. Its "asymmetric" tactics have included protesters super-gluing their fingers to store windows, mass in-store demonstrations, and the hijacking of a Twitter viral marketing initiative by Vodafone which this week resulted in the phone giant posting critical Tweets on its own website.
Unlike the recent student protests or the "hacktivists", UK Uncut is proving adept at securing support across all age groups. John Illingworth, 59, a retired headteacher and former president of the National Union of Teachers, will attend his first protest today. "Everybody who is concerned about what's going on needs to make their voices heard," he said. "Pensioners are being hit very hard by these cuts; even simple little changes will result in thousands of pounds being lost from their pensions."
Among those attending today's protests will be a 75-year-old former accountant from Nottinghamshire. This month a 78-year-old woman called Eileen helped to shut down the Oxford Street flagship store of Topshop, part of Sir Philip's Arcadia Group, which denies any wrongdoing.
Vodafone, which campaigners say escaped payments of up to £6bn this year when it settled a tax dispute with HM Revenue & Customs, said it has become the victim of an "urban myth" and that it is "completely untrue to say that Vodafone has an unpaid £6bn tax bill... Vodafone has not been 'let off' any tax; the company pays its taxes everywhere that it operates."