absent-minded
US /ˌæb.səntˈmaɪn.dɪd/
UK /ˌæb.səntˈmaɪn.dɪd/
1.
having or showing a habitually forgetful or inattentive disposition
:
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He's so absent-minded that he often forgets where he parked his car.
•
Her absent-minded professor walked into the wrong classroom.