The Collaborative International Dictionary of English v.0.48:

Comprehensibly \Com`pre*hen"si*bly\, adv.
   1. With great extent of signification; comprehensively.
      --Tillotson.
      [1913 Webster]

   2. Intelligibly; in a manner to be comprehended or
      understood.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "comprehensibly":
   apprehensibly, articulately, clearly, coherently, definitely,
   distinctly, explicitly, expressly, in plain English,
   in plain terms, in plain words, intelligibly, limpidly, lucidly,
   pellucidly, perspicuously, plainly, simply, unambiguously,
   understandably, unequivocally, unmistakably