IPA: /ˈkwiːziəst/
KK: /ˈkwizēəst/
The most likely to feel sick or uncomfortable, especially in the stomach.
After the roller coaster ride, I felt the queasiest I've ever been.
Comparative: queasier
Superlative: queasiest
The word 'queasiest' is derived from 'queasy' (from Middle English *queis*, meaning uneasy or nauseated) with the superlative suffix '-est' (meaning most). Therefore, 'queasiest' refers to the state of being most uneasy or nauseated.
Think of feeling 'uneasy' or 'nauseated' ('queasy') and remember that 'queasiest' means the most uneasy or nauseated you can feel.