the infiltration of genes from the gene pool of one species into that of another
Origin of introgressionintro- + (di)gression
The movement or spread of alleles of one species into the gene pool of another through repeated backcrossing of interspecific hybrids with members of one of the parental species.
Origin of introgressionFrom Latin intrōgressus past participle of intrōgredī to step in intrō- intro- gradī to step ; see ghredh- in Indo-European roots.
introgress + -ion