IPA: /ˈdʌst.i.ɪst/
KK: /ˈdʌstɪɪst/
The most covered in dust; having the highest amount of dust compared to others.
The dustiest room in the house was the attic, where no one had been for years.
Comparative: dustier
Superlative: dustiest
Dustiest → It is formed from "dust" (from Old English *dūst*, meaning fine particles of matter) and "-iest" (a superlative suffix indicating the highest degree). The word "dustiest" means having the most dust or being the most covered in dust.
Think of 'dust' as fine particles and remember that 'dustiest' means having the most dust.
No commonly confused words.