in Australian slang, nong is used as a pretty mild and/or endearing insult. a bit of a twit, or idiot. nothing too mean or horrid is meant by calling someone a nong.

Generally, a clueless weirdo who is incredibly silly (can have other general meanings).

there are several meanings for a nong...
1. a foolish person who is ill informed of a matter of discussion
2. a individual who argues a matter with such conviction only to find themselves corrected with a single sentence or argument. they are then on labelled as a "nong". in extreme cases of argument, they are named the nongiest of the week.
3. a person who over uses the word "nong" calling it out in totally impertinent situations. the person under direct attack then has the right (almost the obligation) to turn on their attacker and call out "nong!" in a descending tone, the peak of the sound being in the conjunction "no-"

adj/n/v/adv a word with no meaning, used to piss off people with no sense of humor.