Broadway's new spectacle is a cliffhanger - - literally; K2 Drama by Patrick Meyers. Directed by Terry Schreiber.

An intellectual cliffhanger. Fierce forensics at 27,000 feet. A physical production of such stark awesomeness that it impinges on every line and action of the play. Add to these elements a prodigious performance by Jeffrey De Munn and Jay Patterson and you will have some idea of the stunning drama created by Patrick Meyers's ''K2,'' at the Brooks Atkinson Theatre.

Everything in ''K2'' springs from the extreme physical predicament faced by climbers Taylor (Mr. De Munn) and Harold (Mr. Patterson). The two men are stranded on a ledge, 1,250 feet below the summit of K2, the world's second-highest mountain, in the Himalayas between India and Tibet. Harold is immobilized with a broken leg sustained on the night before the long day's action of the play.

The suspense in the ever more taut situation hangs on the question, Will Taylor be able to retrieve from an immediately higher ledge the extra rope needed for both men to reach safety? With only a single rope, Taylor will have to abandon his companion and make the descent alone. In that event, there is no possibility that Harold will survive.

The physical predicament is only the beginning of what Mr. Meyers has in store for his two mountaineers and the audience. Without relaxing dramatic tension, the author launches Taylor and Harold on a series of intense philosophical discussions and deep personal revelations.

Taylor, the cynical pragmatist, lays out a scenario of society's vileness, based on his constant immersion in the criminal scene as an assistant district attorney. His savage indignation is as lacerating as Swift's. From his descriptions, Taylor's relations with women appear to be ugly sexual battles. His Achilles' heel - or perhaps more accurately, his redeeming feature - is his friendship with Harold.

Harold, a one-time dropout-turned-nuclear physicist, cherishes no illusions about the crass world from which they have escaped to these Himalayan superheights. His long speech about a ''gizmo-doodad'' world and the barons who control it is a wildly imaginative flight which Mr. Patterson delivers with relish. But Harold has come to terms emotionally with his own personal need to give and receive affection. Like the altitudes at which they are conducted, these debates are heady intellectual stuff.

Mr. Meyers interrupts them with drafts of oxygen for the climbers and exploits of physical action for the audience. The latter occur when Mr. De Munn, in Alpine climbing gear, scales the sheer face of Ming Cho Lee's ice-encrusted setting to recover the needed rope. Besides these repeated climbs, Mr. De Munn takes a free fall from above the proscenium to just below the narrow ledge which provides the men's precarious refuge.

Mr. De Munn's agility in the performance of these arduous and scary maneuvers adds immeasurably to the excitement of ''K2.'' So does the avalanche with which Mr. Lee heightens the illusion of peril. (A low protective screen at the edge of the stage contains the snow fallout, while spectators are seated no closer than the third row of the orchestra.)

Under the resourceful direction of Terry Schreiber, the performance strikes an admirable balance between Mr. De Munn's abrasive Taylor and the more philosophic Harold of Mr. Patterson. The production is a technical marvel, beginning with the sheer, menacing face of the mountain itself. Allen Lee Hughes suggests the short passage of the mountain day with subtly changing lights. Noel Borden's costumes and gear look as authentic as any in a National Geographic documentary.

''K2'' will be marred for some spectators by Taylor's obsession with obscenities. The script would have been helped by some expletive deletions. But Mr. Meyers has been true to the mountaineers of his drama, as indicated in the following Playbill quotation from James W. Whittaker, the leader of the 1978 American K2 expedition: ''The story of any mountain climb is only in small part about finding routes, fixing ropes, establishing camps, fighting storms, and gaining summits. The real story is the people who do these things.''