You take a thought provoking concept and decide to think extremely deeply about this particular concept. Something which often confuses most people or which has never been/cant be solved. The person thinks about and explores many areas of this concept to such an extent that they feel very mentally exhausted and also may experience a headache. In extreme circumstances epitaxis (a nose bleed) may occur. This can then be compared to the familiar term of wanking where sperm is ejactulated on pleasuring the penis - using the brain to extreme effect that blood is produced (sperm) = brain masturbation(wanking)
the concept of time zones - do you actually live longer if you move from one zone to another, depending on the zone and your place of birth - where brain masturbation originated from
what death feels like
the feeling your brain gets after getting in the frog position, and breathing in and out very deeply for 20 seconds, then standing up very quick and blowing on your thumb very hard.
yo my friend matt just did brain masturbation!