What Is That Thing on the Back of Leonardo DiCaprio’s Head?

The website calls this a "man bun", but it's not a bun at all.  In fact, I don't know WHAT it is.

I'm a girl so I understand that when your hair reaches a certain length it can be hard to keep it out of your face. Like when you're trying to relax on a boat and the wind is whipping it in your face. But I'll be honest I hope I never see a man do this with his hair, even Leonardo Dicaprio. . . .

The issue is NOT that he tied his hair back with a rubber band, the problem is, he doesn't have enough hair, so instead of looking sexy it looks like a silly water spout coming out the back of his head. (Check it out HERE.)

What would YOU call this thing?  And should any man do this, EVER?

Here's a tutorial just in case you wanna look like a goober. . .