smoothen

from WordNet (r) 3.0 (2006)

smoothen
    v 1: make smooth or smoother, as if by rubbing; "smooth the
         surface of the wood" [syn: {smooth}, {smoothen}] [ant:
         {roughen}]
    2: make (a surface) shine; "shine the silver, please"; "polish
       my shoes" [syn: {polish}, {smooth}, {smoothen}, {shine}]
    3: become smooth

from The Collaborative International Dictionary of English v.0.48

Smoothen \Smooth"en\, v. t.
   To make smooth. [Obs.]
   [1913 Webster]