单词：maar 

名词

• 
  [1.n.maar] (同义词:[maar( n. [有时作M-][地]小火山口, 低平火山口 )]  )
• 
  注释列句：a flat-bottomed volcanic crater that was formed by an explosion; often filled with water
• 上位词 -> [volcanic_crater]  [geological_formation(地质层组, 地质组成 )]  [object( n. 物体, 目标, 宾语, 对象 vi. 反对, 拒绝, 抗议 vt. 提出...来反对 )]  [physical_entity]  [entity( n. 实体 )]