Every male in Edom - i. e., every male whom he could find. As did Hadad and his company 1 Kings 11:17, so others would escape in various directions. The Edomite nation was not destroyed on the occasion.
Related Commentaries of 1 Kings 11:16
1 Kings 11:16
16 (For six months did Joab remain there with all Israel, until he had cut off every male in Edom:)