triploid (3n) /trip″loid/ [L, triplus + eidos] , 1. n., an individual, organism, strain, or cell that has three complete sets of chromosomes, triple the haploid number characteristic of the species. In humans the triploid number is 69. It is found in rare cases of aborted or stillborn fetuses. Of triploid fetuses born alive, all are characterized by gross and multiple malformations; they live for only a few hours. 2. adj., also pertaining to such an individual, organism, strain, or cell. Also triploidic. Compare diploid, haploid, tetraploid. See also polyploid. −triploidy, n.