(pejorative) An autistic, or mentally and/or socially impaired person.
noun
5
1
(pejorative) A non-autistic or impaired person whose mannerisms are similar to such people.
noun
4
2
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Origin of rain-man
From the 1988 film Rain Man, about an autistic man.
From
Wiktionary
Rain-man Sentence Examples
You see, those that watched the show believed that Adam himself may be a little autistic, so his mom jumped on the bandwagon stating that she believes her son "…has a little Rain Man in him."
Kim Peek, who was the inspiration for the movie Rain Man is a prodigious savant in fifteen different skill areas.