Which term describes an organism with half the normal number of chromosomes?

The term that describes an organism with half the normal number of chromosomes is monoploid. This refers specifically to a cell or organism that has only one complete set of chromosomes, which is half of the diploid number commonly found in most organisms. In a diploid organism, chromosomes exist in pairs, whereas a monoploid organism has one chromosome from each pair.

In terms of context, diploid organisms have two sets of chromosomes (one from each parent), and triploid organisms contain three sets, which is not relevant to this question about halving. Polyploid organisms have more than two sets of chromosomes, commonly found in plants but not applicable when discussing half the normal chromosome number. Hence, monoploid accurately characterizes organisms with half the typical complement of chromosomes.