IPA: /ˈθɜːr.tɪ.nəs/
KK: /ˈθɜr.t̬si.nəs/
The state of wanting to drink because of a dry mouth or throat.
After running for an hour, I felt a strong sense of thirstiness.
Thirstiness → It is formed from "thirst" (from Old English "þirst", meaning a strong desire for drink) and "-iness" (a suffix indicating a state or condition). The word "thirstiness" refers to the state of having a strong desire for drink or being thirsty.
Think of the strong desire for drink ('thirst') and the state of that desire ('-iness') — that's what thirstiness means.