[1] : WordNet (r) 2.0

clunk
     n : a heavy dull sound as made by impact of heavy objects
         syn: thump, thumping, clump, thud
     v : make or move along with a sound as of a horse's hooves
         striking the ground syn: clop, clump, plunk
see also:
thump thumping clump thud clop plunk 

[2] : Moby Thesaurus II by Grady Ward, 1.0

25 moby thesaurus words for "clunk":
   bump, chink, click, clink, clop, clump, crump, dull thud, flick,
   flump, pad, pat, patter, pitapat, pitter-patter, plump, plunk, pop,
   rap, tap, thud, thump, tick, tinkle, tunk

Clunk >> C Words
Clunk, definition of term: Clunk
clunk_pag1.html