unobservant (adj.)

• careless
• distracted
• distrait
• heedless
• inadvertent
• inattentive
• inconstant
• incurious
• indifferent
• negligent
• noncompliant
• nonconforming
• nonobservant
• regardless
• thoughtless
• unfaithful
• unheeding
• unmindful
• unperceiving
• untrue
• unwatchful