A political system where a monarch acts as head of state within the limits of a constitution.
The United Kingdom is known as a country with a constitutional monarchy.
君主制 is a broader term for monarchy in general, while 立憲王政 specifically refers to a constitutional monarchy where the monarch's powers are limited by a constitution.
Compound of 立憲 (constitutionalism) and 王政 (monarchy). The term is a direct translation of the Western concept of constitutional monarchy.