the son of the British king George III, who was also called George and acted as king from 1811 to 1820 because his father was mentally ill. This period of British history is called "the Regency". When George III died in 1820, the Prince Regent became King George IV.
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.
Dictionary pictures of the day
Do you know what each of these is called?
Click on any of the pictures above to find out what it is called.