IPA: /ˌsɛmioʊˈfɪʃəli/
KK: /sɛmiˈɔfɪʃəli/
In a way that is partly official but not fully recognized as such.
The report was released semiofficially, meaning it wasn't an official government document but still carried some weight.
Semiofficially → It is formed from "semi-" (meaning half or partially) and "official" (from Latin "officialis", meaning pertaining to an office or authority) and the suffix "-ly" (meaning in a manner). The word "semiofficially" means in a manner that is partially official or not fully recognized as official.
Think of 'semi-' meaning partially, and 'official' relating to authority. This helps you remember that 'semiofficially' refers to something that is only partially recognized as official.