Dude, Mark Zuckerberg shitsplained quantum computing on national television for a full 30 mins. As a former quantum physicist it was unbearable because he didn't know what the hell he was talking about.
A condescending, patronizing, arrogant, and, above all, SMUG explanation from somebody who understands almost nothing about a subject but is convinced that he knows more about it than anybody on the planet. The smugness comes from the belief that he is both the world's greatest expert on the topic and, despite (mistakenly) feeling superior to the rest of humanity, is capable of explaining it down to their level.
A shitsplainer is someone who has the smallestunderstanding of a subject, but will still lecture you on it.
A shitsplainer will often ignore what you have to say so they can keep talking.
Jerry saw a Youtube video about politics last night and he spent 30 minutes telling me about how I'm stupid for voting for my party. He's such a shitsplainer.
'Sarah told me all about the economy and how it's getting really bad because economists are stupid. I couldn't get a word in'
'Don't you have an economics degree?'
'Yes, but she read a Buzzfeed article. She's a real shitsplainer'