grey area
noun [ C usually singular ] (US usually gray area) uk/ˌɡreɪ ˈeə.ri.ə/ us/ˌɡreɪ ˈer.i.ə/
灰色地带，灰色区域（指不明朗的形势或规则难界定的领域）
a situation that is not clear or where the rules are not known
The difference between gross negligence and recklessness is a legal grey area. 在法律上，严重过失和鲁莽行事之间的区别尚不好界定。