Vice President Bush, ebullient over his performance in Thursday night's vice-presidential debate, boasted here today that "we tried to kick a little ass last night" in his face-off with Democratic vice-presidential nominee Geraldine A. Ferraro.

Bush appeared to be unaware that he was within earshot of reporters as he made the remark to an official of the International Longshoremen's Association while working a raucous crowd of dockworkers at a GOP rally here. "Whoops, oh God, he heard me," Bush exclaimed when he spotted a television crewman holding a boom microphone. "Turn that thing off."

Minutes earlier, Bush had praised Ferraro to reporters as "gracious" and declined to declare himself the winner.

The remarks were recorded by New York station WNEW-TV, which made them available to other reporters.

Bush defended his remark later at a news conference in Birmingham, Ala., saying it is a common way of expressing victory among athletes. Asked if it would hurt his campaign, he predicted that it would help, adding that he did not intend to apologize to Ferraro.

"I stand behind it, I use it all the time," Bush said of his remark. "My kids use it, everybody who competes in sports uses it." He said Ferraro would understand because "she's a good competitor."

President Reagan, campaigning in Ohio, said he knew nothing about Bush's remark, but "I'm inclined not to believe it."

It was the third time this week that Bush or members of his entourage have uttered controversial remarks aimed at Ferraro. Bush's wife, Barbara, called the House member from Queens "that $4 million -- I can't say it but it rhymes with rich"; and his press secretary, Peter Teeley, on Thursday called her "too bitchy" for voters' tastes.

Mrs. Bush later apologized, saying the word she meant to use was "witch." Asked early today if he thought Ferraro was "bitchy" in the debate, Teeley responded wearily, "I'm going to get some coffee."

Bush's remark contrasted with what appeared to be a carefully orchestrated effort by the Republicans to treat Ferraro with kid gloves. The tone was set at a 6 a.m. briefing in Philadelphia, scene of the debate, when Reagan-Bush campaign chairman Edward J. Rollins said the Democratic contender performed "very, very well," although not as well as Bush, who was "in excellent form."

Rollins had been less charitable Thursday night, saying then that Ferraro turned in a performance befitting a member of Congress from a Democratic district, but not a vice president.

Bush, asked before the GOP rally here to comment on the debate, said:

"I want to say something nice about it . . . . Afterward, she was very gracious -- her family, John Zaccaro and those kids -- and that says something, and it says something nice . . . . And I like that. I thought it was typically American and good for the system and everything else. Nothing personal."

Bush said at the time that he thought the debate "went very well, very well," but he declined to say that he won. "Let's let the American people react without me trying to shape it," he said.

If Bush was outwardly noncommittal about who won, his staff was not. Teeley said of the debate: "One seemed to believe what he was saying. The other spoke as if she'd studied hard and was just going through the motions."

"I expected somebody with a little more life," Teeley said of Ferraro, adding that Rep. Lynn M. Martin (R-Ill.), who played Ferraro in Bush's three practice sessions, was much tougher.

"She was all over Bush like ugly on an ape," Teeley said of Martin.

Teeley, who previously has declined to comment on Bush's aspirations beyond the vice presidency, said he believed the debate performance enhanced Bush's stature as a presidential contender in 1988.

"Anyone who goes through a process like that and comes up a perceived winner does not hurt himself or herself," he said. "It is a plus."

The crowd of more than 2,000 longshoremen who cheered Bush in this heavily Democratic, blue-collar town apparently did not arrive here spontaneously.

Six longshoremen said in interviews with The Washington Post that they were given the morning off, with pay, to attend the rally. Their union, the ILA, has endorsed Reagan. Dockworker Larry Warren said he was paid $16 an hour for coming.

"I'm a token black. They wanted blacks here, and my timekeeper told me if I didn't come I wouldn't get paid," said Warren, a Democrat who said he will vote for Walter F. Mondale.