Principles are the rules you follow because you believe that everyone following those rules would produce a better world.
Meta-principles are the rules for generating principles that you follow because you believe that if everyone generated principles based on those rules, it would create a better world.
For the sake of providing much-needed distance, let us imagine a country with two political parties: the Whigs and the Federalists.
The Whigs’ principles tell them that if someone is fighting for treasured Whig causes, then it is okay to bug their political opponents’ hotel rooms, commit arson, or protest outside of opposed people’s homes with megaphones, or draw a picture of their opponents being killed. Their principles tell them that if everyone was willing to commit those misdeeds in favor of what they consider to be the greater good, the world would be a better place. The Federalists believe likewise, except for Federalist causes.
I imagine that if I told someone that it was unprincipled to do the above listed things, they would say that their principles say that these things are permitted if they are done in pursuit of a noble cause.
If they were operating with Meta-principles, then the Whigs and the Federalists could realize that both of their principles are being generated by the same meta-rule, and that meta-rule is creating a world where the opposing party is doing those things to them as well. Then, if they would prefer neither party do those things than for both parties to do those things, as in the prisoner’s dilemma, they could stop.
If someone says that in fact they would prefer a world where both sides are doing this to each other, than I would say that this may be, depending on the circumstances, Accelerationism, which is a topic for a future essay.
I'd read something more about "Accelerationism"