The Collaborative International Dictionary of English v.0.48:

Clash \Clash\, v. i. [imp. & p. p. Clashed; p. pr. & vb. n.
   Clashing.] [Of imitative origin; cf. G. klatschen, Prov. G.
   kleschen, D. kletsen, Dan. klaske, E. clack.]
   1. To make a noise by striking against something; to dash
      noisily together.
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   2. To meet in opposition; to act in a contrary direction; to
      come onto collision; to interfere.
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            However some of his interests might clash with those
            of the chief adjacent colony.         --Palfrey.
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