When you have an intense discussion about a topic and you get a subsequent mind boner. The excitement and arousal of the mind from entering a heated debate that lends to the feeling of wanting more. Mind boners can also be used to mind fuck people in order to inseminate and propagate ideas. (See also mind fuck)
"Dude that talk last night about the unknown universe gave me the sickest mind boner."
"I totally mind fucked my roommate with my mind boner last night."