[adj] having a chromosome number that is not an exact multiple of the haploid number
ANEUPLOID is a 9 letter word that starts with A.
Biology Dictionary
Definition:
Describes a cell or organism which has an abnormal total number of chromosomes and where numbers of individual chromosomes are out of proportion with the numbers of the other chromosomes. Too many chromosomes is called hyperploidy; too few is called hypoploidy. Aneuploidy is the opposite of euploidy.
WordNet Dictionary