The Collaborative International Dictionary of English v.0.48:

Splashboard \Splash"board`\, n.
   A guard in the front part of vehicle, to prevent splashing by
   a mud or water from the horse's heels; -- in the United
   States commonly called dashboard.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dashboard \Dash"board`\ (d[a^]sh"b[=o]rd`), n.
   1. A board placed on the fore part of a carriage, sleigh, or
      other vehicle, to intercept water, mud, or snow, thrown up
      by the heels of the horses; -- in England commonly called
      splashboard.
      [1913 Webster]

   2. (Naut.)
      (a) The float of a paddle wheel.
      (b) A screen at the bow af a steam launch to keep off the
          spray; -- called also sprayboard.
          [1913 Webster]

   3. an instrument panel beneath the front window of a motor
      vehicle (such as an automobile or truck), containing
      indicating gauges and dials, such as the speedometer and
      fuel gauges, and sometimes certain control knobs or other
      devices.
      [PJC]

WordNet (r) 3.0 (2006):

splashboard
    n 1: protective covering consisting of a broad plank along a
         gunwale to keep water from splashing over the side [syn:
         washboard, splashboard]
    2: protective covering consisting of a panel to protect people
       from the splashing water or mud etc. [syn: splashboard,
       splasher, dashboard]