IPA: /nɒnˈɒbzəvənt/
KK: /nɑnˈɑbzərvənt/
Not paying attention to details or not noticing things around you.
He was nonobservant during the meeting and missed several important points.
Nonobservant → It is formed from "non-" (meaning not) and "observant" (from Latin "observare", meaning to watch or pay attention). The word "nonobservant" means not paying attention or not observing something.
Think of 'not' ('non-') paying attention or 'watching' ('observare') — that's why nonobservant means not observing.