noun
Used as a noun to refer to something brilliant, such as a brilliant idea, performance, or gem. Often appears in compound terms like ブリリアントカット (brilliant cut).
彼のアイデアはまさにブリリアントだ。
His idea is truly brilliant.
このダイヤモンドはブリリアントカットが施されている。
This diamond has a brilliant cut.
素晴らしい is the common Japanese adjective for 'wonderful' or 'splendid', while ブリリアント is a loanword noun used in more specific or stylish contexts.
Loanword from English 'brilliant'.