1. having ones attention or mind or energy engaged

e.g. she keeps herself fully occupied with volunteer activities
deeply engaged in conversation

Synonym: engaged

2. resided in
having tenants

e.g. not all the occupied (or tenanted) apartments were well kept up

Synonym: tenanted

3. held or filled or in use

e.g. she keeps her time well occupied
the wc is occupied

4. seized and controlled as by military invasion

e.g. the occupied countries of Europe