IPA: /ʌnˈmɛnʃənd/
KK: /ʌnˈmɛnʃənd/
Not referred to or talked about; not included in a discussion or list.
There were several unmentioned details in the report that could have changed the outcome.
Unmentioned → It is formed from "un-" (meaning not) and "mentioned" (from Latin "mentio", meaning to mention or refer to). The word "unmentioned" means not referred to or not mentioned.
Think of 'not' ('un-') referring to something that hasn't been 'mentioned' — that's why unmentioned means something that hasn't been talked about.