IPA: //ˌæb.səntˈmaɪn.dɪd//
KK: /ˈæbsəntˌmaɪndɪd/
Someone who is often lost in thought and does not pay attention to their surroundings or what they are doing.
She often appears absentminded when she is deep in thought about her work.
Absentminded → It is formed from "ab-" (meaning away) and "sent" (from Latin "sentire", meaning to feel or perceive) and "-minded" (meaning having a particular mental state). The word describes a state of mind where one is away from the present moment or not fully aware, often lost in thought.
Think of being 'away' ('ab-') from your thoughts and not fully 'feeling' or 'perceiving' what's happening around you — that's what absentminded means.
No commonly confused words.