an unmarried noble
a single person (esp. the rich) who splurges on him/herself
It’s 単身贵族 in Chinese. Obviously, this word refers to single people in comparison to married people who have to devote their time and money to their families. Sometimes, this word is used just as a sugar-coated expression for unmarried people (and hence 独身貴族 are not always as rich as it sounds).
He fully enjoys being single.