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pom-pom

British  
/ ˈpɒmpɒm /

noun

  1. Also called: pompom.  an automatic rapid-firing, small-calibre cannon, esp a type of anti-aircraft cannon used in World War II

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of pom-pom

C19: of imitative origin