irregularity  
noun uk/ɪˌreɡ.jəˈlær.ə.ti/ us/ɪˌreɡ.jəˈler.ə.t̬i/
  (SHAPE)      
  [ C or U ]不规则;不整齐 
the quality of not being regular in shape or form, or an example of this
  The pictures showed cracks and other irregularities in otherwise perfectly regular crystals. 这些图片表明:除了一些裂缝及凹凸不平之处,这些等轴晶系晶体无可挑剔。 
 The west of the island is famous for the irregularity of its coastline. 岛的西部因其曲折的海岸线而著名。 
   (RULE)      
  [ C or U ]违规;不合常规 
something that is not correct or acceptable
  The inspectors found several irregularities in the business accounts. 检查人员在业务账目中发现了几处违规。 
 The irregularity of (= the lack of rules for) English spelling means that it is easy to make mistakes. 英语拼写没有规律可循意味着很容易拼错。 
   (TIME/SPACE)     
 [ U ]不定期;无规律 
the fact that something does not happen at regular times