It's often called "manspreading". You know, when some guy sits in a crowded public space and spreads his legs even further apart than you thought was humanly possible.
I've seen it most often on subways. Perhaps the reason is that few places get more crowded, and in such claustrophobic environments certain males feel the need or imperative to claim territory for themselves. I've even seen dudes trip people or blocking them from getting out of the seats next to them.
Some guys claim they "need" to spread their legs wider than the Grand Canyon. They never say why, but I am always tempted to say that I know for a fact that no man has anything big enough to need that much room!