absentminded

adj.lost in thought; showing preoccupation

"an absentminded professor"

同义词：absentabstractedscatty

1. He is often absentminded, forgetting where he placed his glasses.
   他常常心不在焉，忘记了眼镜放在哪里。
2. The absentminded professor arrived at the lecture without his notes.
   这位心不在焉的教授到讲座时忘记带他的讲义。