The term 'homozygous' means possessing two identical forms of a particular gene, one inherited from each parent. It is often used in the context of disease, for example, in a situation where an individual has inherited a mutant allele or an error in DNA sequence from their mother and they have inherited the identical mutant allele from their father. It's then said that the individual is homozygous for that mutation. They have two identical copies of the deleterious version of that gene and, as a result, will be predisposed to the genetic condition for which the gene codes.

Homozygotes are pure-bred organisms and always produce the same kind of gamete. Compare with heterozygous.