When you find someone incredibly intellectually stimulating and you want them to penetrate your mind further or you wish to penetrate theirs.

Completely intellectual attraction, without physical or emotional attraction. A desire to be mentally close to someone.
The opposite of to wanting to pick your brain ie wanting to have your brain picked
"I met this guy the other day, he's not my type, but the converation is amazing, he really understands me... It's like we were having brainal penetration."
by Moo Lavaca October 26, 2010
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