haploid. 1. having half the number of chromosomes characteristically found in the somatic (diploid) cells of an organism; typical of the gametes of a species whose union restores the diploid number. 2. an individual or cell having only one member of each pair of homologous chromosomes.(hăp′loid′).aploid. 1. having half the number of chromosomes characteristically found in the somatic (diploid) cells of an organism; typical of the gametes of a species whose union restores the diploid number. 2. an individual or cell having only one member of each pair of homologous chromosomes.