1. To instruct or direct someone to return (to some place) to retrieve or accomplish something. The first noun or pronoun can also come after "back." I realized I had left one of the binders for the meeting in the office, so I sent my assistant back for it. The agency is sending me back to the company for a follow-up investigation.

2. To instruct that something be returned (to some place) for some reason or to have something done. The first noun or pronoun can also come after "back." We sent the machine back for some repairs. The customer sent the meal back to the kitchen for being served cold.