Keywords: oblivious, vacant, ignorant, clueless, unaware
Found 2 variants for this sign (click on video to enlarge):
As a Verb or Adjective
To not be aware of something or conscious of what is happening around you. English = (be) oblivious.
To have a look or expression which suggests that you do not understand something or that you are not very intelligent. English = (be) vacant, have a vacant look.