endorsed authoritatively as having met certain requirements; "a certified public accountant"
holding appropriate documentation and officially on record as qualified to perform a specified function or practice a specified skill; "a registered pharmacist"; "a registered hospital"
having quality or payment or delivery guaranteed; "certified milk"; "certified check"; "certified mail"
difficult to penetrate; incomprehensible to one of ordinary understanding or knowledge; "the professor's lectures were so abstruse that students tended to avoid them"; "a deep metaphysical theory"; "some recondite problem in historiography"