unknown origin

US 
UK 
  • un.未明原因
  • Web不明原因;原因不明;来历不明
un.
1.
未明原因

Sample Sentence

Definition:
Category:AllAll,OralOral,WrittenWritten,TitleTitle,TechnicalTechnical
Source:AllAll,DictionaryDictionary,WebWeb
Difficulty:AllAll,EasyEasy,MiddleMiddle,HardHard