While 'Kipedia (and the highest-ranked batch of google results) say it's autism-specific, there is anecdotal evidence of alternate usage. It certainly sounds like it'd refer to more, and the Wikipedia article itself conflates "not on the autism spectrum" with "neurological development and states that are consistent with what most people would perceive as normal, particularly with respect to their ability to process linguistic information and social cues."

There's certainly a lot of confusion and variance in usage within this very thread.