Meta-engineer? Engineering executive? At least he's trying to advance humanity instead of squandering it all on yachts like almost all the rest of the world's billionaires.
Lets be honest, he's kinda transcended all definitions, and that is necessary to be the kind of full picture problem solver that he is... Gain all the information about the problem areas in all contexts from your experts, while having executive authority to execute radical solutions.
I think visionary is the best descriptor and there aren't too many of those folks alive at a given time that are properly placed to execute, and even fewer who actually DO execute.
I was as entranced with the possibility of a permanent extraterrestrial base while watching the presentation last night as I was when I saw the boosters land tandem style in 2018.
What an amazing thing to see happen, the people Elon has brought together have done amazing things on the shoulders of already incredible work.