IPA: /ˌɪn.vɛs.tɪˈɡeɪ.tɪv/
KK: /ɪnˈvɛstəˌɡeɪtɪv/
Relating to the process of examining or looking into something in order to discover facts or information.
The investigative report revealed new evidence about the case.
Investigative → It is formed from "investigare" (from Latin, meaning to track or search into) and the suffix "-ive" (meaning having the nature of). The word "investigative" refers to having the nature of searching or examining closely.
Think of someone who is 'searching' ('investigare') for information — that's why investigative means having the nature of searching.