Source : WordNet®

thudding
     adj : not clear and resonant; sounding as if striking with or
           against something relatively soft; "the dull thud";
           "thudding bullets" [syn: {dull}]

thud
     n : a heavy dull sound (as made by impact of heavy objects)
         [syn: {thump}, {thumping}, {clump}, {clunk}]
     v 1: make a dull sound; "the knocker thudded against the front
          door" [syn: {thump}]
     2: strike with a dull sound; "Bullets were thudding against the
        wall"
     3: make a noise typical of an engine lacking lubricants [syn: {crump},
         {scrunch}]
     [also: {thudding}, {thudded}]

thudding
     See {thud}