Real Dictionary

thud
A thud is a dull sound, such as that which a heavy object makes when it hits something soft.
verb: If something thuds somewhere, it makes a dull sound, usually when it falls onto or hits something else.

thud in American English
a heavy blow
to hit or fall with a dull sound
intransitive verb: to strike or fall with a dull sound of heavy impact
noun: a dull sound, as of a heavy blow or fall

thud in British English
noun: a dull heavy sound
verb: to make or cause to make such a sound