The Collaborative International Dictionary of English v.0.48:

Arietation \Ar`i*e*ta"tion\, n. [L. arietatio.]
   1. The act of butting like a ram; act of using a
      battering-ram. [Obs.] --Bacon.
      [1913 Webster]

   2. Act of striking or conflicting. [R.] --Glanvill.
      [1913 Webster] Arietta