bubblehead

noun3

1. •
   (slang) A stupid person; someone who is empty-headed or oblivious.

   • I rather enjoyed it, but my niece said Audrey Hepburn was a “bubblehead”. — 2004
2. •
   (slang) A submariner; bubble-head.
3. •
   (slang) A navy hard hat or salvage diver.