What is "acroamatical"

Acroamatic \Ac`ro*a*mat"ic\, Acroamatical \Ac`ro*a*mat"ic*al\, a. [Gr. ?, fr. ? to hear.] Communicated orally; oral; -- applied to the esoteric teachings of Aristotle, those intended for his genuine disciples, in distinction from his exoteric doctrines, which were adapted to outsiders or the public generally. Hence: Abstruse; profound.