WASHINGTON (AFP) - Republican White House frontrunner Donald Trump fought off fresh accusations of sexism on Tuesday (Dec 22) after he coined a vulgar new term of abuse while attacking rival Mrs Hillary Clinton.

Whipping up a raucous crowd of supporters in Michigan on Monday (Dec 21) night, Mr Trump's scorn for his Democratic rival took a sexually graphic and personal turn.

Recalling the 2008 presidential race, in which Mrs Clinton lost out to Mr Barack Obama in the battle for the Democratic nomination, the billionaire real estate mogul appeared to reach for a Yiddish term.

"She was favoured to win, and she got schlonged. She lost, I mean she lost," he said, apparently turning the noun "schlong" - a penis - into a verb.

Then, with the partisan crowd cheering him on, he turned to an incident on Saturday (Dec 19) when Mrs Clinton returned late to a televised debate after a bathroom break.

"I know where she went, it's disgusting, I don't want to talk about it," Mr Trump said. "No, it's too disgusting. Don't say it, it's disgusting."

Mrs Clinton did not address Mr Trump's comments directly, but when a young woman at a campaign rally asked her what she would do about bullying, she used the opportunity to launch a not-so-veiled attack on her Republican rival.

"We shouldn't let anybody bully his way into the presidency, because that is not who we are as Americans," Mrs Clinton told a crowd at a school in Keota, Iowa.

Mr Trump returned to the fray on Tuesday (Dec 22) evening with a series of tweets flatly denying any intention to slur Mrs Clinton - and insisting that the offending term was commonplace slang.

"Once again, #MSM (mainstream media) is dishonest. 'Schlonged' is not vulgar. When I said Hillary got 'schlonged' that meant beaten badly," he tweeted.

The campaign trail outburst was not the first in which the thrice-married billionaire real estate mogul appeared to express distaste for women's bodily functions.

In August, Mr Trump triggered outrage when he insinuated that Fox News host Megyn Kelly had subjected him to sharp questioning because she may have been menstruating.

Mr Trump's personal attacks on women also extended to his Republican rival Carly Fiorina, of whom he declared: "Look at that face! Would anyone vote for that?"

His latest remarks drew predictable anger, with liberal site Think Progress dubbing it an "astonishingly sexist attack."

Mr Clinton's team urged supporters to denounce Mr Trump and his belittling remarks.

"We are not responding to Trump but everyone who understands the humiliation this degrading language inflicts on all women should," campaign communications director Jennifer Palmieri said on Twitter.

Mr Trump, a reality television star turned White House candidate, has ridden out all the fury directed his way after previous outbursts.

Polls show the 69-year-old New Yorker remains the frontrunner for the Republican nomination.

His heated rhetoric has infused the campaign, perhaps most notably when he called for a ban on Muslims entering the United States.

Mrs Clinton pounced on those comments during the Democratic debate, saying that Islamic State in Iraq and Syria (ISIS) extremists were using videos of Mr Trump as a recruiting tool.

Mr Trump slammed Clinton as a liar for that remark and demanded an apology.

None was given, but Mrs Clinton did appear on Tuesday to shift her story somewhat about jihadist recruitment efforts.

"If you go on Arabic television as we have, and you look at what is being blasted out, with video of Mr Trump being translated into Arabic - 'No Muslims coming to the United States,' other kinds of derogatory, defamatory statements - it is playing into the hands of the violent jihadists," she said.

Mr Trump's speeches are often unscripted, and supporters applaud him for what they see as his authenticity and disdain for political correctness.

A new survey, however, shows that those voters who have not been won over are turned off by his bombast.

Fifty per cent of registered US voters said in a Quinnipiac poll on Tuesday that they would be "embarrassed" to have Mr Trump as president, compared to 23 per cent who would be proud.

If Mrs Clinton were elected, 33 per cent would be proud and 35 per cent would be embarrassed, according to the poll.

Quinnipiac has Mr Trump leading Republicans with 28 per cent support, followed by Senator Ted Cruz at 24 per cent and Senator Marco Rubio at 12.