'Vagrancy' is the state of having no home and no work, and wandering from place to place — and, in the older law books, the crime of doing so. For a long time in Britain and America there were 'vagrancy laws': if the police found you sleeping in the street, with no money and no job, they could arrest you for vagrancy itself, not for anything you had done to anyone. That is the sense the dictionary is giving you here. You should know that this is now mostly a historical and legal word. Many of those laws have been struck down or quietly dropped, because people came to see that punishing someone for being poor is not really justice. So today you meet 'vagrancy' in three places: history books, legal writing, and news stories arguing about how cities treat homeless people. In ordinary conversation nobody says it — a modern speaker says 'homelessness'. And the two words are not the same in feeling: 'homelessness' points at a problem people are suffering, while 'vagrancy' points at a person being blamed. Choose carefully.

遊蕩罪、流浪（舊法律上的罪名：無家、無業、在街上遊蕩本身就構成犯罪）；現代談街友議題一般用 homelessness 無家可歸