IPA: /ʌnˈfɔːrθˌkʌmɪŋ/
KK: /ʌnˈfɔrθˌkʌmɪŋ/
Not willing to provide information or help; reserved or uncooperative in communication.
The witness was unforthcoming during the investigation, refusing to answer many questions.
Unforthcoming → It is formed from "un-" (meaning not) and "forthcoming" (from Old English "forðcuman", meaning to come forth or to appear). The word "unforthcoming" means not coming forth or not being open or forthcoming in communication.
Think of 'not' ('un-') being open or 'coming forth' — that's why 'unforthcoming' means not being open or not sharing information.