/ ˈdʌmdʌm; NAmE / (also ˌdumdum ˈbullet ) noun
a bullet that spreads out and breaks into many pieces when it hits sb
ORIGIN: It is named after the factory at Dumdum near Calcutta in India, where such bullets were originally made. They are now illegal.
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WORD ORIGIN
late 19th cent.: from Dum Dum , name of a town and arsenal near Calcutta, India, where such bullets were first produced.