IPA: /ʌnˈmɛltɪd/
KK: /ʌnˈmɛltɪd/
In a solid state and not changed into a liquid by heat.
The ice cubes remained unmelted in the cooler all day.
Unmelted → It is formed from "un-" (meaning not) and "melted" (from Old English "meltan", meaning to soften or dissolve). The word "unmelted" means not having been softened or dissolved.
Think of 'not' ('un-') having 'melted' — so unmelted refers to something that has not been softened or dissolved.