Ostmark is a term that refers to a former administrative district in Austria. It was used during the Nazi regime to refer to parts of Austria that were considered to be part of the greater German Reich. Synonyms for ostmark include Eastern March, Eastern Austria, and Ostland. Other terms that could be used to refer to the same geographical region are Austro-Hungarian Empire, Austrian Empire, and Habsburg Empire. However, these terms historically refer to different periods of time and may not be interchangeable. Ultimately, the use of synonyms for ostmark may depend on the context in which they are being used.