IPA: /ʌnˈraɪpənd/
KK: /ʌnˈraɪpənd/
Not fully developed or matured; still in an early stage of growth.
The unripened fruit is too sour to eat.
Unripened → It is formed from "un-" (meaning not) and "ripen" (from Old English "ripian", meaning to become ripe). The word "unripened" means not yet ripe or not having reached maturity.
Think of something that is 'not' ('un-') 'ripe' — that's why unripened means it hasn't matured yet.