I think we're well served by distinct language:

  * "intelligent" is the intellectual capacity one is born with
  * "stupid" is the failure to use that intellectual capacity

> I know plenty of very intelligent people who have been quite stupid at times. I know that while I may have adequate intelligence I've certainly been stupid more than once (or maybe even twice).

I call those people skilled instead of intelligent.

That is not the "stupid" used in this context.