IPA: /ʌnˈpʌblɪzaɪd/
KK: /ʌnˈpʌblɪˌzaɪd/
Something that has not been made known to the public or has not received public attention.
The unpublicized event was a surprise for everyone involved.
Unpublicized → It is formed from "un-" (meaning not) and "publicize" (from Latin "publicus", meaning public, and the suffix "-ize", meaning to make). The word means not made public or not announced to the public.
Think of 'not' ('un-') making something 'public' ('publicize') — that's why unpublicized means it hasn't been shared with the public.