Let me set the stage. A microservice is a self-contained(!) application that handles a single(~) small(~) business capability of a bigger system.
DDD is an idea that we shouldn't concentrate on technology, but use the actual domain to build our applications. Using the same language (words) and behavior (functionality) that are present / inherent in the domain.
A "bounded context" is again a self-contained, well-defined part of a business domain with its internal language and functionality. It is self-contained, because it doesn't need any "words" (things) from other contexts to make sense. It is well-defined, because it has explicit "bounds".
Neither of these has anything to do with how things are persisted. "Entities" are not database records, they are things that have their business-behavior as per the context they are in.
With that said, a single object can only belong in one context per definition. Rare exceptions may apply for objects explicitly made for communication between services.