意为“聚集起来；集中；聚集”。如：
the mass media 大众媒体
Mass education is essential in promoting democracy.
民众教育对提倡民主是非常重要的。
We want to promote literacy on a mass scale.
我们要大规模地提高文化水平。
Dark clouds massed and we expected rain. 乌云密布,看起来就要下雨了。
【高考链接】
The young dancers looked so charming in their beautiful clothes that we took _____ pictures of them.  (上海2003)
A. many of  B. masses of  
C. the number of D. a large amount of
【简析】
A项中many后of多余。C项中应该把the换成a。D项修饰不可数名词。pictures为可数名词，应用masses of（既可接可数名词，也接不可数名词）。 故选B。