1.Definition: befitting or belonging to an emperor or empress

"Imperial palace"

2.Definition: belonging to or befitting a supreme ruler

"Golden age of imperial splendor"

Related Adjective(s):majestic, purple, regal, royal

3.Definition: of or belonging to the British Imperial System of weights and measures

4.Definition: relating to or associated with an empire

"Imperial colony", "The imperial gallon was standardized legally throughout the British Empire"