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1.
A combination of the two word parts: 'pseudo', meaning 'like' or 'the same as', and 'kin', meaning 'family'. In reference to your best friend, especially in a mixed gender relationship. A showing of friendly love or affection without the hint of romantic attraction that other words such as 'love' portray. To transliterate, it means 'like/as family'. It is what you substitute for sister and brother, but meaning the same, sans blood relation.
Example:

"Hey, pseudokin, what's shakin'?"

Sincerely yours, -pseudokin

etc....
by Slick Sauce March 01, 2012