皇帝陛下

Noun

 * 1) Imperial Majesty; Your Majesty the emperor
 * 2) Your Majesty; His Majesty; Her Majesty

Etymology
From compound  +, with a compound meaning of “emperor of everything under the throne”.

Noun

 * 1) imperial majesty

Usage notes
As a title or term of reference, the term is much more common.