IPA: //ʌnˈsuːtɪd//
KK: /ʌnˈsutɪd/
Not appropriate or suitable for a particular purpose or situation.
He felt unsuited for the role of a leader because he preferred to work alone.
Comparative: more unsuited
Superlative: most unsuited
Unsuitable is formed from "un-" (meaning not) and "suited" (from the Old French *suiter*, meaning to follow or be appropriate). The word "unsuited" means not appropriate or not fitting for a particular purpose or situation.
Think of 'not' ('un-') being added to 'appropriate' or 'fitting' ('suited') — that's why unsuited means not fitting for something.