A similar word is doofus http://learnersdictionary.com/definition/doofus

In my mind a dingus is a person who does ridiculous things, acts strangely. edit: NO, I don't think the person is clumsy. They act silly or act stupid to get attention or just because they like to, not because they are clumsy. I think the definitions in this urban dictionary explain it pretty well: https://www.urbandictionary.com/define.php?term=dingus

I'm not sure - I suspect that is US-only slang. I think it means a clumsy person. (similar meaning TO...)