thudding

(verb) make a dull sound. Synonyms: thud, thump. Example: "The knocker thudded against the front door."

(verb) strike with a dull sound. Synonyms: thud. Example: "Bullets were thudding against the wall."

(verb) make a noise typical of an engine lacking lubricants. Synonyms: crump, thud, scrunch.

(adj) not clear and resonant; sounding as if striking with or against something relatively soft. Synonyms: dull. Examples: "The dull thud." "Thudding bullets."