Noun, verb, adjective, adverb, interjection.
Narfage is what I like to call a "filler" word. When you have nothing else to say, just drop it into the sentence. It can mean anything you want it to.
Why you gotta go an' do that narfage?
Narfage! I ruined the day by wearing the polka dot bikini from target.
I totally narfaged up that test.
Is to used by the speaker when one has either nothing to say or is in any type of sad, happy, humorous, etc. mood. Although is mostly used to "spice" up a sentence
I want my stinkin' lousy breakfast!
This lollipop tastes narfagey.