The Definition of Done is a shared understanding of what it means for work to be complete, and to ensure transparency. The Scrum Guide states that "The Developers are required to conform to the Definition of Done, as defined by the Scrum Team. If there are multiple Scrum Teams working together on a product, they must mutually define and comply with the same Definition of Done."1 This means that the Product Owner does not have the final say over the Definition of Done, but rather collaborates with the Developers and the Scrum Master to agree on the quality standards and expectations for the product.
References:
* 1: The Scrum Guide2, page 14
* 2: The Scrum Guide