WordNet sense 1 (a compact mass):

ball, chunk, clod, glob, lump

WordNet sense 2 (a grouping of a number of similar things):

bunch, cluster, clustering

WordNet sense 3 (a heavy dull sound (as made by impact of heavy objects)):

clunk, thud, thump, thumping

WordNet sense 4 (make or move along with a sound as of a horse's hooves striking the ground):

clop, plunk

WordNet sense 5 (come together as in a cluster or flock):

flock, constellate

WordNet sense 6 (walk clumsily):

clomp

WordNet sense 7 (gather or cause to gather into a cluster):

bundle, bunch up