DPMO stands for 'Defects Per Million Opportunities'. 'Opportunity' means the opportunity for a defect, one unit may have many opportunities for a defect.
DPMO is a Six Sigma Metric. Six Sigma process improvement projects aim to achieve 3.4 or fewer Defects Per Million Opportunities. Using DPMO, rather than the proportion of defective items, gives a common standard that can be usedto compare the defect rates of simple and complex items.