street urchin       
noun [ C ] /ˈstriːt ˌɜː.tʃɪn/ us/ˈstriːt ˌɜ˞ː.tʃɪn/
 流浪儿童,流浪街头的孩子
a child who is poor and does not have a home, living and sleeping on the streets of a city
  They are street urchins living alone in an abandoned car under an expressway. 他们都是流浪儿,独自生活在高速公路下一辆废弃的汽车里。 
 - More examples
 - He arrived at the orphanage as a ragged, malnourished street urchin.
 - A street urchin swiped his phone.
 - The film's title "Slumdog Millionaire" refers to Jamal, a street urchin who winds up a contestant on a game show.
 - Packs of ragged street urchins roamed around trying to pickpocket businessmen.