Thud
Part of speech: noun
Definition: The sound of a dull impact. Republic F-105 Thunderchief jet ground attack fighter, after the sound it makes when it crashed into the North Vietnamese countryside, due to its high rate of loss.
Part of speech: verb
Definition: To make the sound of a dull impact.
Thump
Part of speech: noun
Definition: a blow that produces a muffled soundthe sound of such a blow; a thud
Part of speech: verb
Definition: to hit (someone or something) as if to make a thumpto thud or poundto throb with a muffled rhythmic sound