复数
a structure or object that impedes free movement
any condition that makes it difficult to make progress or to achieve an objective
同义词：roadblock
anything serving to maintain separation by obstructing vision or access
英汉双解词典包含3185865条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。