The Collaborative International Dictionary of English v.0.48:

Boation \Bo*a"tion\, n. [L. boatus, fr. boare to roar.]
   A crying out; a roaring; a bellowing; reverberation. [Obs.]
   [1913 Webster]

         The guns were heard . . . about a hundred Italian
         miles, in long boations.                 --Derham.
   [1913 Webster]