"Dead on arrival," abbreviated "DOA," is originally the phrase used by hospitals and police, for a patient who was probably still alive when they were put into the ambulance, but dead when the ambulance reached the hospital.
For products like electronics, it means that the product never worked. The shipment arrived, the customer opened the box, and the product didn't work at all. It is a description that might be used when returning a product or filing a complaint about it. One might imagine a return from with some checkbox alternatives:
REASON FOR RETURN
[ ] DOA
[ ] Damaged in shipment
[ ] Missing parts (please specify)
[ ] Wrong color
[ ] Wrong voltage
[ ] Incompatible (please include details)
In speaking, the initialism is pronounced as three separate letters, one after the other, quickly: "dee-oh-ay."
In U.S. politics, a bill must be passed by both houses of Congress, and the phrase is often used to describe a bill that has been passed by one house but has no chance at all of being passed by the other. For example, "Senator X said, 'If the House passes the bill in its current form, it will be DOA in the Senate.'"