The world, says this year’s Tate Triennial curator Nicolas Bourriaud, has just entered a new era: altermodernity. The old postmodernism and its focus on identity politics is dead, he argues; culture has gone global. Artists -- Bourriaud calls them homo viators -- are now free to navigate among unlimited geographies and borrow from unlimited histories. It’s all about transition, rootlessness, flexibility, the moveable feast, as Ernest Hemingway termed it (back in the 1920s).

To many this will sound like a textbook definition of postmodernism, but if there is something the French art theorist is good at, it’s (re)branding. Bourriaud’s 1998 book Relational Aesthetics, which coined a phrase for art practices based on social interactions, propelled him to international stardom and triggered years of exegeses. Postproduction (2004), an understanding of the artist’s practice as the "deejayeeing" of cultural signs (through appropriation or "sampling"), may have had less of an impact, but the art world has grown to love the curator’s reduction of difficult-to-grasp contemporary phenomena to a few catchy terms. So much so that the numerous issues that Bourriaud’s proposition of the "altermodern" raises -- including the crucial question of who has access to this privileged global mobility -- seem to have been swept under the carpet in order to indulge the sexiness of the new phrase.

Just as the Whitney Biennial attempts to picture the state of American art at a certain moment in time, so the Tate Triennial has traditionally done for British art. But for this edition, Bourriaud has expanded his purview to include "passers-by" along with British residents -- that is, essentially, anyone (not too different, in fact, than Chrissie Isles and Philippe Vergne’s 2006 experiment with a "post-national" biennial at the Whit). In this time of "transnational" art, the relevance of the idea of a local scene certainly needs to be addressed, even if doing so means running the risk of showcasing the usual suspects. The curator negotiates this difficulty pretty well in "Altermodern," which though it includes its share of biennial regulars -- Franz Ackermann, Tacita Dean, Mike Nelson and Subodh Gupta, among others -- nonetheless manages to fill out its roster of 28 artists with plenty of talent new to the international art circuit.

And as much as the Tate Triennial 2006 was about quiet formal elegance, the 2009 version is defined by its exuberance. The museum’s neoclassical main gallery is taken over by a thrift fair-like display that prominently features Ruth Ewan’s "world’s largest accordion," a giant instrument on which political songs from the artist’s archive are played daily by two volunteers.

Also on hand are David Noonan’s freestanding cut-out figures, a sombre bunch, and Bob and Roberta Smith’s retro faux slogans. This last, a perfect example of the artist’s signature retro shop sign esthetic, is replaced by a new one every Friday, in a weekly update of his often ironic concerns (the first one reads, "I wish I could have voted for Barack Obama").

Gupta’s spectacular Line of Control (2008), a huge atomic mushroom made of stainless steel kitchen utensils, not-so-subtly evoking the nuclear threat on the sub-continent, provides a focal point for this visual abundance. In the other rooms, the atmosphere is slightly more contained, but the feeling of raw energy remains.

Rabelaisian, grotesque and delightfully absurd, Nathaniel Mellors’ Giantbum (2009) is certainly one of the Triennial’s highlights. Made of two films and shown in a dark and woolly projection room, the piece follows a theater company rehearsing and enacting a scene about a bunch of characters lost in a giant’s entrails, their leader traumatized by an experience of coprophagy.

Entirely removed in register, Lindsay Seers’ grainy film Extramission 6 (Black Maria) (2009) interweaves images of the artist performing with a lamp stuck on her forehead with interviews with members of her circle of friends. Meant to play out Seers’ desire to be altogether a projector and a camera, the work is a wonderful moment of poetical self-investigation.

Other highlights include Charles Avery’s installation of drawings and oversized monster-head sculptures, which document the fantastic territory of his ongoing project The Islanders; Shezad Dawood’s hour-long feature film deftly mixing the genres of Western and horror movies; and Walead Beshty’s delicate prints of film stock photographed as it passed through an airport’s x-ray machines, displayed with an array of glass cubes, variously cracked while in transit. Whether or not these and other works fit the altermodern bill -- or whether a term so inclusive can have any use or significance beyond the celebration of its own coining -- remains up for discussion.

COLINE MILLIARD is a writer based in London.