dissimilation

from WordNet (r) 3.0 (2006)

dissimilation
    n 1: a linguistic process by which one of two similar sounds in
         a word becomes less like the other; "the Old French MARBRE
         became the English MARBLE by dissimilation"
    2: breakdown in living organisms of more complex substances into
       simpler ones together with release of energy [syn:
       {catabolism}, {katabolism}, {dissimilation}, {destructive
       metabolism}] [ant: {anabolism}, {constructive metabolism}]

from The Collaborative International Dictionary of English v.0.48

Dissimilation \Dis*sim`i*la"tion\, n.
   The act of making dissimilar. --H. Sweet.
   [1913 Webster]