Rosie O'Donnell Rosie O'Donnell

Rosie O'Donnell is not going to let an insult from Republican presidential candidate Donald Trump go unchecked - but she's not going to stoop to his level either.

Trump, who has famously feuded with O'Donnell for the better part of a decade now, was asked by moderator Megyn Kelly during the first GOP debate Thursday night about his penchant for referring to women he didn't like as "fat pigs, dogs, slobs and disgusting animals."

"Only Rosie O'Donnell," Trump blurted out, before Kelly could finish her sentence.

O'Donnell, who was clearly tuned into the debate, responded almost immediately via Twitter - and then, presumably, dropped the mic.

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It was the only comment O'Donnell posted for the duration of the debate.

Trump and O'Donnell's public dislike of each other dates back to 2006, when O'Donnell, who was then a co-host of The View, criticized Trump's handling of Miss USA Tara Connor's drug abuse controversy and questioned why a man who left his first wife after having an affair should consider himself "the moral compass for 20-year-olds in America."

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Trump, with characteristic subtlety, responded by calling Rosie "fat," "a real loser," and "a woman out of control" in a statement to People.

"Loser" is Trump's preferred term for O'Donnell, which he has used in several tweets related to her since then, including one expressing sympathy for O'Donnell's then-fiancée, Michelle Rounds.

O'Donnell's response on Thursday night is perhaps most notable for its restraint. Granted, it's not exactly difficult to out-class Trump, whose campaign highlights thus far have included referring to Mexicans as drug addicts and rapists, and releasing the private cell phone number of GOP rival Lindsey Graham. But kudos to O'Donnell for taking the high road.