Which definition best fits the word 'urbane'?

The definition that best fits the word 'urbane' is indeed associated with sophistication and smoothness in manner. This term describes someone who is polished, refined, and exhibits a certain elegance in their behavior and speech, typically as a result of social exposure and education. An urbane individual often navigates social situations with ease and charm, making them appear cultured and self-assured. The essence of 'urbane' captures a cosmopolitan quality, suggesting a person who is both knowledgeable and gracious in various societal contexts. This aligns perfectly with the notion of sophistication, thus making it the most accurate definition.