enclosed in a protective covering; sometimes used in combination; "his sheathed sword"; "the cat's sheathed claws"; "a ship's bottom sheathed in copper"; "copper-sheathed"
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"