Congress flinched in its big confrontation with President Reagan yesterday and agreed to his proposal for a timeout: a brief extension of government spending authority to be followed by another deadline-defying battle over spending cuts next month.

Bereft of weapons, Democrats responded with a barrage of words.

One Democrat spoke of the "Reagan theater of the absurd," and another accused the president of staging a "manufactured shootout at the O.K. Corral." House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) said Reagan's depth of knowledge about the budget was "an absolute and utter disgrace."

The plan--approved 221 to 176 by the House and 88 to 1 by the Senate--restored the flow of money into the government until Dec. 15 and cleared the way for both Reagan and Congress to take off on Thanksgiving vacations.

But the action means that Congress will have to produce spending cuts satisfactory to Reagan within three weeks or go through a repeat of the ordeal it just endured in trying to beat Reagan at the veto game. And the next time Congress' Christmas recess will be at stake along with the solvency of the government.

After Reagan's early-morning, well televised veto of the big new stopgap spending bill that Congress had approved Sunday night, Congress had little choice but to adopt the spending cuts he wanted or reinstate and extend the old spending authority that had expired at 12:01 a.m. Saturday.

Congress clearly lacked the two-thirds vote of both Houses to override the veto, as House Democratic leaders acknowledged when they made no override attempt and simply shunted the veto message off to committee.

So the only remaining immediate question was how long the extension would be.

Republicans, pushing to enact Reagan's own spending priorities as soon as possible and win a political victory for the administration, wanted no later than Dec. 15. Democrats, happier with spending levels as they were and anxious to avoid a public relations victory for Reagan, wanted an expiration date of Feb. 3.

But even O'Neill indicated that the fight had gone out of the Democrats when, after warning that Congress would regret another spending fight just before its Christmas recess, he told the House he was "not going to shed any tears" if he lost.

"There's not victory out there for anyone," he said ruefully.

Rep. Silvio O. Conte (R-Mass.), ranking Republican on the House Appropriations Committee, appeared to agree. "We're the laughingstock of the nation . . . let's get it over with and let's go home," said Conte, warning that setting an expiration date beyond Dec. 15 would invite another veto and further stalemate this week.

Then House Minority Leader Robert H. Michel (R-Ill.) made the House an offer it couldn't seem to resist. If the House would accept the December date, which the Republican Senate majority was already supporting, "then I'm inclined to think you're free to leave for Thanksgiving."

If that wasn't enough, Conte picked up a hint dropped by a Democrat concerned about money for Public Health Service hospitals in Boston, Seattle, Baltimore and New York and offered to include funding for them in the Republican proposal--an offer that appeared to be good for at least a few votes.

When House Appropriations Committee Chairman Jamie L. Whitten (D-Miss.) complained, Conte grinned and said, "It's just too bad you didn't think of it, Jamie."

In the midst of it all came a complaint from Rep. Gerald B. H. Solomon (R-N.Y.) that the timing was being influenced by plans by Rep. Joseph P. Addabbo (D-N.Y.) to go on a two-week, government-paid Appropriations Commiteee trip to Italy. Democrats groaned, and Conte, joined by Rep. Millicent Fenwick (R-N.J.), leaped to the defense of both the committee and Addabbo, chairman of its defense subcommittee. The purpose of the trip is largely to examine earthquake relief efforts and "it's no junket," Conte said.

Ignored in the rush to end the exhausting crisis of the last three days was a warning from O'Neill that if Congress had to adopt another spending resolution on Dec. 15 "you'll be in exactly the same position on the eve of Christmas as you were on the eve of Thanksgiving."

By this he meant that the dispute over spending cuts will be no less intense in December than it was in November, with Democrats insisting they had met Reagan's targets and the administration contending that Congress missed by a mile.

By late yesterday, the Office of Management and Budget was saying that Congress had given Reagan only $1.3 billion of the $8.4 billion in domestic appropriations cuts that he wanted, even less than the $2 billion that OMB had counted on Sunday.

But OMB's computations, coupled with what O'Neill called Reagan's "flaky" economics, drew charges yesterday from Democrats that Reagan was pumping up a crisis over less than $2 billion out of a more than $400 billion spending program to camouflage failure of his economic policies.

"If there's been any budget busting, it has been the president's deliberate action in bringing on a recession . . . ," O'Neill said. "The current recession is a direct result of the tight money and flaky economics of the president's own administration."

Responding to Reagan's claim that Congress hasn't passed a budget for the year, O'Neill said the Democratic House has passed 12 of 13 appropriations bills and stalled on the foreign aid bill only because of opposition from Republicans.

As for Reagan, O'Neill said the president can't even "carry on a conversation about the budget." Reagan "knows less about the budget than any president in my lifetime," said O'Neill, who came to Congress during the Eisenhower administration.

Rep. Richard A. Gephardt (D-Mo.) told reporters he thought Reagan may want continued stalemate over the budget "to keep the issue alive . . . so he can blame Congress." Added Gephardt: "Either there was a lot of miscommunication or willful confusion of the issue so there would be no agreement."

The plan adopted yesterday continues spending levels imposed Oct. 1 when the new fiscal year started with no regular appropriations bills in place--the same spending levels that expired after midnight Friday. It also provides pay retroactively to government employes for work over the three-day funding hiatus, according to Senate Appropriations Committee chairman Mark O. Hatfield (R-Ore.).

Democrats argued that because the old levels anticipate $27.3 billion less spending over a year's period than the vetoed bill would have provided, an extension to Feb. 3 would have saved more money than an extension to Dec. 15.

The problem for Reagan is that most of the savings--about $25 billion, according to Conte--would come from defense spending, which Reagan wants to increase while cutting domestic social programs.

Democrats countered with the argument that a 50-day extension through Feb. 3 would have saved about $4 billion which, ironically, is what has been described as Reagan's "bottom line" demand for domestic appropriations savings for the year.

In the Senate, only Minority Whip Alan Cranston (D-Calif.) voted against the Dec. 15 termination date. Among Washington-area House members, the vote was along party lines. In Sunday's vote on passage of the spending bill, Sens. Charles McC. Mathias (R-Md.) and John W. Warner (R-Va.) voted for it, while Sens. Harry F. Byrd Jr. (Ind.-Va.) and Paul S. Sarbanes (D-Md.) voted against it. In the House, Rep. Frank R. Wolf (R-Va.) was the only Washington-area member to vote no on passage of the bill.