verb phrase. Go postalish, if not postalish-bionic.
Real citation: “I ruin everyone i've ever dated i never leave a guy and have them either not cry, breakdown, go mentalish or go cold and any combination you'd like to throw in there of all those.”
(July 9, 2007, Nexopia, http://www.nexopia.com/weblog.php?uid=672501)
Made-up citation: “As I write this, my batshit dog is going mentalish because his fluffball friend doesn't want to play. I swear, he could wear out five fluffballs a day; I should rent him out."