increase in the number of haploid sets (23) of chromosomes in a cell. Triploidy
refers to three whole sets of chromosomes in a single cell (in humans, a
total of 69 chromosomes per cell); tetraploidy refers to four whole sets
of chromosomes in a single cell (in humans, a total of 92 chromosomes per
Definition from: GeneReviews
from the University of Washington and the National Center for Biotechnology Information
Having or being a chromosome number that is a multiple greater than two of the monoploid number.