A dull sound without resonance, like that produced by striking with, or striking against, some comparatively soft substance; also, the stroke or blow producing such sound; as, the thrud of a cannon ball striking the earth.

To make, or strike so as to make, a dull sound, or thud.

The F-105 Thunderchief was always called the Thud by those who flew it. It was a single-engined jet fighter-bomber that carried the major load of strikes against North Vietnam.

a heavy dull sound (as made by impact of heavy objects)