Internet slang from the late 2000s, now mainstream-casual. Says the speaker felt 'struck by lightning' - usually from cringe, absurdity, or shock rather than awe. The corresponding verb is 雷到, as in 我被雷到了 'I was floored.' Avoid in formal writing.
memory
雷 = 'thunder/lightning' + 人 = 'person.' Picture being zapped by a bolt of lightning the moment you read or hear something - that's the feeling 雷人 captures.
