IPA: /ˈθɜːrstiər/
KK: /ˈθɜrstiər/
Having a strong desire for water or other liquids; feeling the need to drink more than usual.
After running in the hot sun, I felt thirstier than ever.
Comparative: thirstier
Superlative: thirstiest
Thirstier → It is formed from "thirst" (from Old English "þirst", meaning a strong desire for drink) and the comparative suffix "-ier" (meaning more). The word "thirstier" means having a greater desire for drink than usual.
Think of feeling a stronger desire for a drink — that's what 'thirstier' means, as it indicates being more thirsty.