单词：glacial_period 

名词

• 
  [1.n.glacial_period] (同义词:[ice_age(n.[地]冰河时代(在新生代的第四世),冰期,冰川期 )]  [glacial_period(n.[地]冰川时期 )]  [glacial_epoch(n.[地]冰川时期 )]  )
• 
  注释列句：any period of time during which glaciers covered a large part of the earth's surface; "the most recent ice age was during the Pleistocene"
• 上位词 -> [period( n. 时期, 学时, 节, 句点, 周期, （妇女的）经期 adj. 过去某段时期的 int. 没有了 )]  [geological_time]  [time]  [attribute( n. 属性, 品质, 特征, 加于, 归结于 )]  [abstraction( n. 提取 )]  [entity( n. 实体 )] 
• 部分总称 -> [prehistory( n. 史前史 )] 
  所有总称 -> [prehistory( n. 史前史 )]