IPA: /ˌʌndərprɪˈpɜːrd/
KK: /ʌndərprɪˈpɛrd/
Not sufficiently ready or equipped for a task or situation.
She felt underprepared for the exam despite studying all night.
Underprepared → It is formed from "under-" (meaning below or insufficiently) and "prepared" (from Latin "parare", meaning to make ready). The word "underprepared" means not sufficiently ready or lacking adequate preparation.
Think of being 'below' ('under-') the level of being 'ready' ('prepared') — that's why underprepared means not ready enough.