It could be a noun, verb, adjective, or explative... definitely used contextually... It's almost like a cross between the exaggerated teenage angst-ridden "I KNOW..." and the genuine educated yet somewhat sarcastic adults "Thank-you~" -- yet with a slight twist... It somehow got breeded with the term "Whatever!" and now resides in the bowels of Urban Dictionary, of all places. There's only one thing to say about this, you guessed it!! "NGYANGYOW!!!
-- response?? -- 'ngyangyow.
2) Dude!! I caught a delicious bass -- oh nevermind... <-- 'ngyangyow.
3) The phone rings... 'ngyangyow. (maybe thats how you can perfectly answer telemarketers...)
4) Meow, Meow!! Captain Crunch Whistle!! Meow meow Federal Bureau of Investigation, Meow!! (maybe you can just appreciate the concept, here, 'ngyangyow.)
5) the examples are simply listless, 'ngyangyow.
1) n. extremely non-plussing information
2) n. an extremely non-plussing person
3) excl. a perfect response to such non-plussingness
2 "man, that guy is such a 'ngyangyow!"
3 Jack:"Dum-de-dumm blah blah... I'm a butt-sniffing circus bear." Buddy:"...'ngyangyow."
As an exclamation, it is also quite handy/appropriate when walking around someone just standing in public for no apparent reason. Like a person (who gives an impression they most likely don't understand the local language very well) at your grocery store, half blocking the entrance/exit. When you walk around them instead of saying "excuse me!", you give an understanding nod and say "...'ngyangyow."