Top Definition
means adult in japanese. often used to describe anime pornography (it is NOT hentai. Hentai is a kanji (compound word) of the words Hen (strange, weird) and Tai (behavior, attitude, appearence etc etc) It is always used to describe a person and NEVER anime or manga) If someone was going to point out anime pornography, they would say "seijin-anime" or "seijin-manga". NOT "hentai"
average schmuck: hey man did u see that hentai NG is advertising?
smart person: its not hentai its seijin.
average schmuck: oh realy? I didnt know that
by G-Imago130 July 10, 2006
Seijin (星人, Star-people), which roughly translates 'Alien', are extra-terrestrial beings that originate from their respectively named planets, or are otherwise sentient aliens as opposed to simple Space Kaiju.

In neo-kaiju toys, this generally refers to sentient aliens.
Baltan is definitely my favorite seijin from Ultraman.

Have you seen the new glow-in-the-dark seijin release by Elegab? It's a lottery, so get your email in quick.
by hellointerloper December 27, 2014
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