New orders for "big ticket" durable goods increased 8.3 percent in November, the first advance since August and the biggest since September 1980.

Economists said the increase reflected renewed growth in the economy after the recent slowdown.

More than half of the increase resulted from the placement of orders for defense capital goods. But excluding defense, new orders for items including appliances, automobiles and factory equipment increased 3.3 percent, the first gain since July. The figures are all seasonally adjusted.

The Commerce Department said new orders for manufactured durable goods -- products expected to last three or more years -- increased by $7.9 billion to $104.0 billion last month, the first gain since the 0.3 percent increase in August. New orders rose by 8.5 percent in September 1980.

"This is another sign that the economy has restarted" after the growth slowdown of the third quarter, said Allen Sinai, chief economist of Shearson Lehman/American Express Inc.

The nation's gross national product slowed to a weak 1.6 percent growth rate in the third quarter and has been estimated at 2.8 percent this quarter.

The nondefense increase was one of "several signs of renewed life in the economy," Sinai said, predicting that the index of 12 leading economic indicators will show a 1.3 percent increase for November when that measure of the economy's health is released next week.

Robert Ortner, chief economist for the Commerce Department, said the index will be "well over 1 percent . . . and that augurs well for the economy as we enter 1985."

The number of durable goods orders can vary greatly from month to month, so one report alone does not indicate a trend, analysts said, emphasizing that the report has greater significance in the context of other improvements in the economy.

Recent growth in income, retail sales, building permits, employment, money supply and durable goods orders, combined with continued low inflation and declining interest rates show that "we've finished the worst of the growth slowdown," Sinai said.

Retail sales increased 1.8 percent in November and personal spending on both goods and services went up 0.9 percent last month, the Commerce Department reported earlier.

Consumer prices rose 0.2 percent in November, the smallest monthly increase since June. By Thursday, all of the nation's top 15 banks had cut their prime lending rates by a half-point to 10.75 percent.

"A reason for believing that these signs of life will have staying power over the next six months . . . lies in the easing of monetary policy by the Fed Federal Reserve Board ," Sinai said.

The nation's basic money supply, known as M1 and representing funds readily available for spending, increased by $3.8 billion in the week ended Dec. 10, the Federal Reserve said Thursday.

The White House hailed the durable goods report as "another sign that the economy is growing, that people have confidence about the economy," said spokesman Marlin Fitzwater. "I realize a good part of the increase was for defense but, nevertheless, a lot of new orders are being placed.

"It gives us a bright horizon for next year's economy," Fitzwater said.

The National Association of Manufacturers was more guarded. "The number is not very significant," said Jerry Jasinowski, chief economist for the association.

The durable goods report "doesn't mean much because most of it is in defense, and the nondefense increase is almost all catch-up in last month's decline," Jasinowski said. He added, however, that "things are picking up -- the worst of the slowdown is probably over and the economy ought to begin gradually picking up now" and continue improving next year.

An increase in orders for factory orders is considered a sign of the strength of overall demand because those kinds or purchases usually require financing and pre-planning.

The $9.8 billion increase in orders for defense hardware reflected a rebound from an abnormally low level of $4.9 billion in October, analysts said.

Shipments of manufactured goods, another key business indicator, increased 1.6 percent in November, by $1.7 billion to $102.1 billion, the highest level since August. Shipments of transportation equipment increased 3.7 percent, almost entirely because of growth in the auto industry.

Unfilled orders held by durable goods manufacturers increased 0.6 percent, by $1.9 billion to $346.3 billion. But without the increase in the defense capital goods category of $3.5 billion, unfilled orders declined 0.7 percent, the fourth consecutive decline since July.