Source : Webster's Revised Unabridged Dictionary (1913)

Sedimentation \Sed`i*men*ta"tion\, n.
   The act of depositing a sediment; specifically (Geol.), the
   deposition of the material of which sedimentary rocks are
   formed.

Source : WordNet®

sedimentation
     n : the phenomenon of sediment or gravel accumulating [syn: {deposit},
          {alluviation}]