What does "undress" mean?

Additional senses

1. 2.(Med.) To take the dressing, or covering, from; as, to undress a wound.
2. 3.A loose, negligent dress; ordinary dress, as distinguished from full dress.
3. 4.(Mil. & Naval) An authorized habitual dress of officers and soldiers, but not full-dress uniform. Undress parade (Mil.), a substitute for dress parade, allowed in bad weather, the companies forming without arms, and the ceremony being shortened.