adjective.
Having a single set of unpaired chromosomes, as in a germ cell, such as an egg or sperm, or in a moss plant or a drone bee.
noun.
An organism having haploid cells.
the GNU version of the Collaborative International Dictionary of English
adjective.
having half the number of chromosomes normally present in somatic cells; having only one chromosome of each type, and therefore having only one complete set of genes; Contrasted with diploid and polyploid. See also diploid.