Holding a rank of nobility — being a lord, a lady, a duke, a countess, a baron, and so on. In Britain these ranks are inherited or given by the monarch, and someone who has one is 'titled': 'a titled family', 'she married a titled man', 'the titled classes'. It says something about birth and social position, not about work, so a person is not 'titled' for being a professor or a general. The word often comes with a small flavour of old money and old England, and writers use it to raise that whole world in one word. Careful: there is a completely separate everyday use of 'titled' meaning 'having the name' — 'a book titled War and Peace', 'a song titled Yesterday'. Same spelling, different job, and context makes it clear which one you mean.