This is a compound word that I honestly did not know the English equivalent to until rather recently. Hokori means “dust,” and darake as a suffix means “full of,” so put together, it literally means “full of dust,” or simply “dusty.”
My mom used this word often in terms of things in the house that, obviously, hadn’t been dusted. In my mind, hokori-darake refers to something that is covered in dust to the point you can write your name in it. I used to imagine that the dust particles that danced in the air in a beam of sunlight were atoms.