You can use the adjective vacant to describe something that is empty — an apartment with no tenant or furniture, a job with no worker, or a person with no brainpower.
Vacant has its roots in the Latin word meaning “empty” or “free.” It can mean “unoccupied,” such as that seat next to you on the train — even if you’ve put your coat there. A vacant look or stare, however, is one that shows no intelligence or the slightest spark of interest. One might find this vacant gaze in the eyes of a zombie or in the eyes of a teen who has spent the past five hours gaming.
