sporadic       
adjective uk/spəˈræd.ɪk/ us/spəˈræd.ɪk/
 偶尔发生的;阵发性的;断断续续的
happening sometimes; not regular or continuous
  sporadic gunfire 零星的炮火 
 a sporadic electricity supply 不稳定的电力供应 
 More than 100 people have been killed this year in sporadic outbursts of ethnic violence. 今年有超过100人在零星爆发的种族暴力中丧生。 
 Synonym: occasional
Compare: continualcontinuous adjective (NOT STOPPING)