The Collaborative International Dictionary of English v.0.48:

Cavernous \Cav"ern*ous\, a. [L. cavernosus: cf. F. caverneux.]
   1. Full of caverns; resembling a cavern or large cavity;
      hollow.
      [1913 Webster]

   2. Filled with small cavities or cells.
      [1913 Webster]

   3. Having a sound caused by a cavity.
      [1913 Webster]

   Cavernous body, a body of erectile tissue with large
      interspaces which may be distended with blood, as in the
      penis or clitoris.

   Cavernous respiration, a peculiar respiratory sound andible
      on auscultation, when the bronchial tubes communicate with
      morbid cavities in the lungs.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cavernous
    adj 1: being or suggesting a cavern; "vast cavernous chambers
           hollowed out of limestone"
    2: filled with vascular sinuses and capable of becoming
       distended and rigid as the result of being filled with blood;
       "erectile tissue"; "the penis is an erectile organ" [syn:
       erectile, cavernous]

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "cavernous":
   abysmal, abyssal, boat-shaped, boatlike, bottomless, bowl-shaped,
   bowllike, cavelike, commodious, concave, concaved, craterlike,
   cup-shaped, cupped, cymbiform, deep as hell, dish-shaped, dished,
   dishing, dishlike, fathomless, funnel-breasted, funnel-chested,
   funnel-shaped, gaping, hollow, hollowed, incurved, incurving,
   incurvous, infundibular, infundibuliform, navicular, naviform,
   plumbless, plunging, retiring, retreating, reverberant,
   saucer-shaped, scaphoid, scyphate, sepulchral, soundless,
   spoonlike, sunk, sunken, unfathomable, unfathomed, unsounded, vast,
   without bottom, yawning