1. 逃亡者を捕まえるため、あるいは検問などで通りや道路の交通を止めるために警察によって置かれる障害物(a barrier set up by police to stop traffic on a street or road in order to catch a fugitive or inspect traffic etc.)
2. 進歩や目的達成を困難にする状況(any condition that makes it difficult to make progress or to achieve an objective)