1.
Something between nasty and naughty... but that is neither of the two
You have very nafty thoughts
See naughty, nasty, dirty, kinky, sexy
2.
Meaning quite the opposite of "nasty", which this word is commonly related to, it is an acronym for "nifty as fuck", it began as simply "naf", (i.e. "that burrito was pretty naf, man.") however upon making the word available with more ease, the suffix "-ty" was added on. Thus changing the acronym from "naf" to "nafty", giving it better use as it was intended, as an adjective. This is used to describe something seen as good, or as a more extreme form of "nifty".
If zombies were going to attack, I think we could set up a pretty nafty Zombie Smasher vehicle. It could run on zombies.
See nifty, as, fuck, nasty, bad ass, kick ass, amazing, awesome, great, successful, nappy
3.
turrible,difcuftin',awful
thif bloody corpfe iv nafty