IPA: /ʌnˈhiːtɪd/
KK: /ʌnˈhitɪd/
Not warmed up or made hot.
The unheated room was quite cold during the winter.
Unheated → It is formed from "un-" (meaning not) and "heated" (from Old English "hǣtan", meaning to make warm or hot). The word "unheated" means not made warm or not hot.
Think of 'not' ('un-') making something 'warm' ('heated') — that's why unheated means something that is not warm.