unobservant
1. [ adjective ] not consciously observing
Synonyms: unseeing
Examples:

"looked through him with blank unseeing eyes"

Related terms: unperceptive
2. [ adjective ] not paying attention
Synonyms: unvigilant unwatchful inattentive
Related terms: unalert
Similar spelling:   unobservable
  unobserved
  unbiased
  unfocused
  unabashed