While reporting for NBC News on Tuesday, Williams, 53, reluctantly mentioned Trump's tirade on-air.
"Donald Trump, who has driven well past the last exit to relevance and peered into something closer to irresponsible here, is tweeting tonight," the journalist said. An exasperated Williams then referenced a few of Trump's tweets and said, "That happened," before moving on to other election night news.
Williams' on-air quip provoked the Celebrity Apprentice host to lash back -- at length! -- the next day via Twitter.
"Brian Williams knows that I think his newscast has become totally boring so he took a shot at me last night," Trump sniped. "The only thing more boring than Brian Williams' newscast is his show Rock Center, which is totally dying in the ratings—a disaster! Brian Williams, wouldn't you love to have my ratings?"
He then began defending his disappointment over Obama, 51, defeating Republican challenger Mitt Romney, 65.
"This was the Republicans election to win. Mitt Romney is a good man but he just never connected with the people," he argued. "The voting booth process was a total disaster -- it could and should be much better and more efficient -- tremendous room for error!"
But then he moved back to bashing Williams.
"Brian -- Thanks dummy -- I picked up 70,000 twitter followers yesterday alone. Cable News just passed you in the ratings," Trump tweeted. "Brian, I hope NBC Nightly News isn't paying you too much -- look at what's happening to nightly news."
"Brian Williams was never a smart guy but always passes himself off as such. People will learn the truth!," he added. "Brian, if I'm "well past the last exit to relevance" how come you spent so much time reading my tweets last night?"
Trump then concluded, "Another four years--not good for the country but we'll have to live with it! Our country is totally split right now but someday it will come together! We have to make America great again!"
"It's freezing and snowing in New York," he noted of the nor'easter hitting the Big Apple over a week after Superstorm Sandy devastated the area. "We need global warming!"
Watch Brian Williams' report on Trumps' Twitter tirade in the video above.