If you find something ~, you do not understand it or do not know how to deal with it.
It took years to understand many ~ diseases...
= puzzling
ADJ: usu ADJ n
If you find something ~, you do not understand it or do not know how to deal with it.
It took years to understand many ~ diseases...
= puzzling
ADJ: usu ADJ n
Collins COBUILD. Толковый словарь английского языка для изучающих язык Коллинз COBUILD (международная база данных языков Бирмингемского университета) . 2012