recondite
adjective formal uk/ˈrek.ən.daɪt/ us/ˈrek.ən.daɪt/
深奥的;玄妙的;晦涩的
not known about by many people and difficult to understand
We had to work from material that was both complex and recondite. 我们不得不从那些复杂晦涩的资料着手开始工作。
Synonym: abstruse