The Collaborative International Dictionary of English v.0.48:

Rasher \Rash"er\ (r[a^]sh"[~e]r), n. [In sense 1, probably fr.
   rash, a., as being hastily cooked.]
   1. A thin slice of bacon.
      [1913 Webster]

   2. (Zool.) A California rockfish (Sebastichthys miniatus).
      [1913 Webster]