Source : Webster's Revised Unabridged Dictionary (1913)

Bombilation \Bom`bi*la"tion\, n.
   A humming sound; a booming.

         To . . . silence the bombilation of guns. --Sir T.
                                                  Browne.

Source : WordNet®

bombilation
     n : sound of rapid vibration; "the buzz of a bumble bee" [syn: {buzz},
          {bombination}]