As you “SO?!” so shall you threap.
To threap is to make a threap, but not to make a threat – you are not talking of action, you are taking action, and the action is disagreement. You may threap a person, in which case you are rebuking or scolding the person; you may simply threap, in which case you are arguing, bickering, or wrangling about terms; or you may threap that something is so, in which case you are maintaining your position in the face of contradiction or doubt.
Let us imagine a case, let’s say a spokesperson, whom – to spice things up – we may call the Grim Threaper. He is representing some enthroned mammothrept who has not thruppence worth of thrift, but the Grim Threaper has heard that you have said as much, and he calls you out from the throng. He threaps you: you are a very naughty person for threatening the mammothrept’s reputation for thrift. You clear your throat and throw in some facts. He threaps: that is a manner of speaking, and besides the mammothrept did not mean what he said or say what he meant, and in any case he did not say what he said. Your temples start to throb but you thrust forth your evidence. He threaps that it is not so: the mammothrept is the chieftain of thrift. And so the Grim Threaper makes a threepeat, three threaps… but he may threap-eat yet when all is laid on the table (and why not – threptic has to do with eating and nutrition), so he ought to have put more honey on his tongue.
There are more ways you can use threap, too. You can threap someone out of something – wear them down with incessant argumentation. You can threap something upon someone – press it on them, urge that they accept it. You can threap someone down – prevail in discourse through threaping (“A man will say of a clamorous talker, he did not convince me, but he threaped me down” —Richard Winter Hamilton, Nugæ Literature, 1841; thanks to the OED for that and much of the rest of this information).
In short, threaping is badgering, bullying, talking a blue streak, and thereby prevailing or at least attempting to prevail. The word does not have the same bludgeoning bluntness as words that begin with b, and perhaps that is a weakness for modern use: thr can have driving force – thrusting, throwing, thrilling – but the vowel is too high (the same as in “three”) and thereby weak-seeming.
At any rate, you seldom see it. Well, I think it is nonetheless a useful word, one that can come in quite handy in our times. Allow me to insist and to persuade you…