A neurotypical (NT) is someone whose neurochemistry and neuroanatomy is typical of the population at large. It's used to separate "normals" from those of us on the autistic spectrum, seen as better from our point of view than calling them "normal" (leaving us, of course, as "abnormal"). Some folks on the spectrum, especially those with Kanner's autism or those old enough to have experienced the psychopharmaceutical reaction to ASD, do use the term as a pejorative, because of the bitter experiences they've had with NTs.
The term was first coined in the '60s, by a group of LSD users who believed that pharmaceutical alteration of their perceptions had led them to some "greater truth", and had at the same time permanently altered their neurochemistry. (They were right about that last, to a point, but for the most part, it wasn't for the better.) When autistic activism began, pretty much (AFAIK) at the same time as the addition of Asperger's Syndrome to the DSM (Diagnostic and Statistical Manual - the "gold standard" reference for psychological and neurological disorders), activists seized on the term as a quick way of dividing "us" and "them". (George Carlin once observed that people are okay, taken two or three at a time; beyond that number, they start to choose up sides and wear armbands.) It's now fallen into common use in the ASD community as shorthand for "those so-called 'normal' people over there".
Enough?
It's definitely answered my question, lol. Thanks!