Zend is another word for being depressed.. When your feeling down, and u feel like the whole world is going against you.. You're friends and family hates u, and you're just a loner
An act of laughing so hard at someone's jokes even if they aren't funny, often symbolizing some sort of infatuation for that someone.
It was first encountered on Jimmy Kimmel where Zendaya would go laugh extremely hard over Tom Holland's stories that haven't even gotten to the punchline yet.