A shitpost is hard to classify, but it is usually an off-topic post intended to derail, hijack, circlejerk, or otherwise spam a conversation.

I don't have any examples of Palmer shitposting, because his scheme never really got off the ground. A generic example of a shitpost would be if say, someone posted in this thread this image: http://i.imgur.com/QoZHVLs.jpg and demanded that we only post spiderman memes, instead of talking about the intended topic.