polyploid Syllabification: (pol·y·ploid)Pronunciation: /ˈpäliˌploid/ BiologyDefinition of polyploid adjective (of a cell or nucleus) containing more than two homologous sets of chromosomes. (of an organism or species) composed of polyploid cells. noun a polyploid organism, variety, or species. Derivatives polyploidy noun polyploid in other Oxford dictionaries Definition of polyploid in the British & World English dictionary