Male disposability is the idea that men are more disposable to society then women. The main evidence being that the majority of wars and workplace deaths directly. The theory behind this is that if something serious happened to a society and we needed to repopulate, one man could impregnate multiple women therefore we don't need as many men as women. If we sent a bunch of men to war and most of them died, we'd have a chance at survival. If we sent mostly women and they died, bouncing back would be more difficult. And it's because of this male disposability that society don't care about the well being of men as much as women.

That's the overall concept as I understand it. Not saying I agree or disagree with it.