The behavior that has been seen exhibited by Donald J. Trump, particularly noticeable during the time of his hold of the office of President of the United States whenever events unfolded that he wasn't particularly pleased with. Examples of this behavior include Twitter-Rampages, signing of an inordinate number of executive orders, publicly smearing his opponents, etc.
A Trump impersonator depicted a humorous interaction of 45 in the Oval office. Poor Donnie didn't like it and threw a Trumper-Tantrum all over Twitter about it.
The Trump Administration didn't like that he lost the 2020 election so he's throwing an epic Trumper-Tantrum about it rather than concede the office and provide for a smooth and seamless transition.
A Trump-fueled, conspiracy-riddled, emotionally-charged, childish, volatile, irrational, innappropriate, disrespectful, display of dangerous foolishness, most often done by the Cult of Personality of Donald Trump, the MAGA mob.
(Insurrection Day, Jan.6th, 2021, would be the "Trumper-Tantrum of Terror".)
The Pastor at my local church is having a Trumper-tantrum about simple, temporaryhealth measures, like wearing a mask.
When a grown man overhears something mean said about him, and proceeds to go on a poorly-articulated, juvenile rant on Twitter at 3am.
"Did you see that SNL said something mean about Emperor TinyHands McThinskin again?"
"I figured, there was another late-night Trumper Tantrum making the country look stupid again."