You keep using that word, but I do not think that it means what you think that it means.
Thus spake the Spaniard in The Princess Bride and thus my rant at friends who have used the term Postmodern in my presence.
About 5 or 10 years back I started hearing this term bandied about by smarter-than-me friends. And I asked in my thoughtful way, "wuzzat." The response would generally be something I didn't quite follow about rejecting the metanarrative. I became an engineer because I meta narrative, several in fact, in Literature class that didn't make sense. Thus, I went around asking folks who seemed to be smarter than me, "wuzzat," in the hope of finding one enough smart enough to use terms I could understand.
I'm not a complete dullard, having a passing familiarity with trends in western civilization. I'd actually read Modern Art and the Death of a Culture and Goedel, Escher, Bach or at least enough to claim a passing familiarity therewith. So, I knew there was this Thing called The Enlightenment (which was important because they capitalized it), wherein folks thought that thought sufficed to find truth, perfect themselves, and perfect society. I've always thought Reason was reasonable, so I went along with this Enlightenment thing for the most part. I didn't really follow that New Soviet Man thing, but what can you expect of a Fundamentalist.
Since I trained as a mathematician and had an interest in the Foundations of Mathematics, I knew a bit about what Goedel did with axiomatic systems. He proved there are limits to reason: any axiomatic system big enough to do arithmetic leads naturally to a theorem that resembles the Liar's Paradox. The theorem said in hifalutin terms, "This theorem is unprovable." If the theorem is true, the axiomatic system is incomplete; if the theorem is false, the axiomatic system is inconsistent. Reductio Ad Absurdum. (Has to be provound, it's both capitalized and it's Latin.)
My liberal writing friend cites this and says, "Hah, I told you you can't know truth." He's one of the guys who tried to tell me what Postmodernism is. Of course, the existence of places where reason is unreasonable does not imply that reason is unreasonable in every place. It seems Dr. Goedel's math proof didn't show it was unreasonable to balance your checkbook.
I say all this to say that to understand Postmodernism, you must understand Modernism and that means understanding the Enlightenment and how it died. I place the moment of that death in the 1920s. Others place the moment of Modernism's death with the fall of the Berlin Wall (as Modernism's most ghastly construct died).
MY definition of "postmodernism" is whatever follows Modernism. It isn't a positive movement, per se, as much as a negation of Modernism. Modernism required logical consistency, Postmodernism does not. This explains why Postmodernism embraces ecclecticism. Once you prove Reason (capitalized) doesn't suffice to obtain Truth (also capitalized), it's a short step to say that there is no Truth. Or that anyone who claims to have Truth is playing a power game. This leaves the Postmodernist with a real problem with Authority.
That's probably why I never got a Satisfactory Answer when I asked what Postmodernism is. There's no Postmodernist authority who can give an answer that is true. Thus here's MY ANSWER as to what Postmodernism is: It's whatever follows Modernism. It rejects Reason's ultimacy; it is skeptical about Truth; it extracts meaning directly from Stories as the listener/reader interprets it individualistically.
I figure Postmodernism is a mere transitional device serving to digest the corpse of Modernism, rendering it into rich fertile soil from something as significant as The Enlightenment will grow that I'll call post-Postmodernism for now. Metaphorical maggots. When the bones of the corpse of Modernism is completely picked clean, Postmodernism will be gone, too.