The term that describes an organism with two different alleles for a trait is heterozygous.

Here's a breakdown:

* Allele: A specific version of a gene.

* Heterozygous: Having two different alleles for a particular gene.

* Homozygous: Having two identical alleles for a particular gene.

For example, if a flower has one allele for red petals (R) and one allele for white petals (r), it would be heterozygous for flower color.