IPA: /ˌɪnəʊˈzɜːrvənt/
KK: /ɪnˈoʊbərvənt/
Not paying attention to things around you; failing to notice or observe details.
He was inobservant during the meeting and missed important information.
Inobservant → It is formed from "in-" (meaning not) and "observant" (from Latin "observare", meaning to watch or pay attention). The word "inobservant" means not paying attention or not observing something carefully.
Think of 'not' ('in-') paying attention or 'watching' ('observare') — that's why inobservant means not observing.