You can delete a batch workflow status only when it has no associated steps, and there are no existing batches in the status you are trying to delete.
To delete a batch workflow status, from the Batch Entry page in Administration, click Batch workflows under Configuration. The Batch Workflows page appears. Click the name of a workflow to go to its record. From the batch workflow record, in the Step 1: Define status values used with the workflow grid, click the double arrows next to a status to expand its row. On the action bar, click Delete.