Source : Webster's Revised Unabridged Dictionary (1913)

Landslip \Land"slip`\, Landslide \Land"slide`\, n.
   1. The slipping down of a mass of land from a mountain, hill,
      etc.

   2. The land which slips down.

Source : WordNet®

landslip
     n : a slide of a large mass of dirt and rock down a mountain or
         cliff [syn: {landslide}]