"She's 'Crooked Hillary' and I say that I will beat her easier than beating some of the people that I've just won (against)," Trump told Fox News host Bill O'Reilly.
After his Super Tuesday victory, Trump said Clinton, the Democratic front-runner, was playing "the women's card"
in her campaign, and added that if she were a man she would only have 5% of the vote.
He reprised that attack on Thursday night, saying, "She's playing the woman card. It's the only thing she's got going."
Asked earlier in the day by NBC's "Today" show host Savannah Guthrie if he understood why some people found the remarks about Clinton demeaning, Trump responded: "No, I find it to be a truthful comment. I think that the only thing she's got going is that she's a woman. She has done a terrible job in so many different ways."
Trump was also asked about Wednesday's foreign policy speech in which he vowed to be an "unpredictable" president when it comes to military policy.
"The enemy is watching every move we say, every move we do militarily. We announce what we are doing and they prepare for it," Trump said. "I don't want that ... We need unpredictability. We need to be unpredictable. We're so totally predictable."
Trump also said he would not rule out the use of nuclear weapons in the fight against ISIS.
"I will be the last to use it. I will not be a happy trigger like some people might be," Trump said, taking a veiled jab at GOP rival Ted Cruz and his call to "carpet bomb" ISIS. "I will be the last. But I will never rule it out."
Thursday night, he dismissed any suggestion of pulling Americans troops out from Afghanistan.
"You have to stay and do the best you can, not that it's ever going to be great," Trump told O'Reilly, explaining that its proximity to nuclear-armed Pakistan makes a U.S. presence there necessary.
"I don't think you have a choice," Trump said.