A bathroom inside a bedroom doesn't have a special name. But when you're talking about rooms in a house, it's common for the biggest bedroom to be labelled the "master bedroom" and in modern houses most master bedrooms usually include a dedicated bathroom, but not always. In an architect's drawing, that room might be labelled the "master bath" but this is not a common term to use. This answer is about what you call rooms in someone's house. The terminology is different when you're talking about hotel rooms.

A bathroom directly connected to a bedroom is often called an en-suite bathroom . And an en-suite bathroom attached to two bedrooms is sometimes referred to as a "Jack and Jill bathroom". Sometimes we call a bathroom adjacent to or directly connected to a master bedroom in a private home a master bathroom . Master bedroom is a large room delicated for heads of the house ( usually husband and wife ) . :)

a bathroom inside a bedroom is called an en-suite

Master bedroom, master bath. Not to be confused with....