A dude from the Warhammer 40k universe. Twentieth son of some magnificent shiny dude who's in charge of everything, the primarch of the Alpha Legion of SPEEHS MARINES along with his twin brother, Omegon. Everyone has an obsession in pretending to be him because his legion is specialized in manipulation, covert operations and pretending to be Alpharius.
Random dude:" I am Alpharius!"
Another random dude:"No, I am Alpharius!"
by ClearlynotAlpharius September 28, 2018
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A twin who masquerades as their sibling in order to have sex with their sibling’s spouse. Not to be confused with any astrology terminology.
Person 1: “So, how’d your date go last night? Did you finally get down and dirty with him?”

Person 2: “Ughhh, no! It turns out I wasn’t having a date with HIM, but his TWIN BROTHER instead! God, what an Alpharius!”

Person 1: Really?! Wow, you’re right, he’s totally an Alpharius…”
by Blackwatch Kaide July 11, 2023
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