A Shadowban is an excuse trolls and sad people use to justify why no one bothers to read, reply or like the content that they post online. They assume that it must be because their content is hidden from public view, in fact they're just boring.
I know for sure I've been shadowbanned because hardly anyone comments or likes my posts on Twitter. It's definitely a shadowban conspiracy because I know, I'm like, genius, and everyone would be amazed by my super-radical views.