A dumdum or a dumdum bullet is a bullet that is very soft or hollow at the front. Dumdum bullets cause large and serious wounds because they break into small pieces and spread out when they hit someone.
dumdum in British English
(ˈdʌmˌdʌm)
noun
a soft-nosed or hollow-nosed small-arms bullet that expands on impact and inflicts extensive laceration
Also called: dumdum bullet
Word origin
C19: named after Dum-Dum, town near Kolkata (Calcutta) where these bullets were made