Unless I’m mistaken, the term is much more specific than that : it denotes people who have significant mental issues except for a specific, usually narrow thing they can do at virtuoso level. Think Rain Man.
Person.
Everyone seems to be ignoring the pejorative – ‘spaz’. As a shortened form of ‘spastic’ It doesn’t really contain the definition within it – i.e. is a “spastic geek”, or “intellectual, but such a spaz”. However, it seems to have the connotation – mostly when someone is called a ‘spaz’ on media, there’s a strong geek stereotype associated with it. I’m thinking of the Eugene-type character, as you might find in the film Grease, who’s constantly mocked but at the very end, can out throw the Greasers at the fair, even if he can’t pass them in the hallway without getting tripped up.
I think you will find that spaz is an unacceptable word these days.