Shortened version of boy friend or girl friend (not to be confused with boyfriend/girlfriend). The origin comes from saying "boy space friend or girl space friend" so as not to be confused with a significant other. Basically, the definition of friend zoned.
The absolute closest person in the world to you. Someone you have told all of your secrets to and aren't uncomfortable in any way, shape, or form when with them. They are closer than a best friend, a sibling, and even a significant other.
John: Hey, is that your boyfriend
Laura: No, that's my space friend
by Rubikscuber April 20, 2015
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A girl who is a friend but NOT a girlfriend (one that's actually in a relationship) and often implied to be one.

May or not be a "friend with benefits"
Jason: Hey is Jake actually seeing Katie?

Cole: Naw, she's just his girl space friend.
by Sensi the Sensei January 30, 2010
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