look up any word, like demisexual:
1) a playfull insult between friends
2) a person who gets really horribly drunk on a regular basis
1) shaun, pick it up ya mash head!
2) Johny Mase stop drinking you mash head!
by BaBs February 09, 2004
When you and your buddies whip out your fatties and joust with them.
Eric and Jason were quite excited and decided to mash heads about it.
by DongToucher August 23, 2011