thud (v.)

Old English þyddan "to strike, stab, thrust, press," of imitative origin. Sense of "hit with a dull sound" first recorded 1796. Related: Thudded; thudding. The noun is attested from 1510s as "blast of wind;" 1530s as "loud sound."

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Definitions of thud from WordNet
thud (v.)
make a dull sound;
the knocker thudded against the front door
Synonyms: thump
thud (v.)
strike with a dull sound;
Bullets were thudding against the wall
thud (v.)
make a noise typical of an engine lacking lubricants;
Synonyms: crump / scrunch
thud (n.)
a heavy dull sound (as made by impact of heavy objects);
Synonyms: thump / thumping / clump / clunk