1. To use something absorbent to clean the inside of something. A noun or pronoun can be used between "swab" and "out." Did you hear me? I said go clean your room! Do you need to swab your ears out? The doctor carefully swabbed out the wound and then rinsed it with a saline solution.
2. To use something absorbent to clean dirt or other contaminants out of something. A noun or pronoun can be used between "swab" and "out." It always makes me gag to see him swabbing wax out of his ears like that. Make sure you carefully swab out all the dirt before you apply the bandage.
swab something out
to wash or wipe something out in order to make it clean. The doctor swabbed my ear out carefully. The doctor swabbed out my ear carefully.
To clean the inside of something with a swab: I used this cloth to swab out the rifles. The doctor swabbed my ear out.