Preoccupied means so absorbed in your own thoughts or concerns that you barely notice what's happening around you. When your mind is completely focused on something (often a worry or problem), you become preoccupied.

A student preoccupied with an upcoming presentation might walk right past their best friend in the hallway without saying hello. They're not being rude; their mind is just somewhere else entirely. A parent preoccupied with work problems might stare at dinner without tasting it, lost in thought about tomorrow's meeting.

The word suggests complete mental absorption. Someone who's preoccupied is mentally tied up with their concern. You can see it in how they respond slowly to questions, forget what they were saying mid-sentence, or need you to repeat yourself.

People become preoccupied with all sorts of things: an upcoming competition, a disagreement with a friend, excitement about a trip, or figuring out a tricky math problem. The feeling usually lifts once you resolve whatever was occupying your mind.