flâneur       
noun [ C ] (also flaneur) uk/flænˈɜːr/ us/flænˈɜ˞ː/
 游手好闲的人;悠闲的人
someone who walks around not doing anything in particular but watching people and society
  She wanders around with her camera, a flâneur with a keen eye. 她带着照相机到处逛,游手好闲却眼光敏锐。 
 Lisbon is a city built for the ultra-relaxed, aimless flaneur. 里斯本是为极度放松、漫无目的的悠闲人士所建造的城市。 
 - More examples
 - The artist depicts herself as a melancholy urban flâneur.
 - The flâneur was born in Romantic poetry - the Wordsworth of The Prelude as well as Baudelaire.
 - He explores the neighbourhood with the experienced, imperturbable eye of a flaneur.
 - These were the districts which novelists, flaneurs and artists had explored for their poetic obscurity.