The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]