The beneficial effect on the phenotype of crossing (hybridization) upon growth, vigor, and physical or mental qualities in a strain of plants or in animal stock, as measured by the difference between the midparent mean phenotype and that of F1; also referred to as hybrid vigor. [hetero- + -osis, condition]
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het·er·o·sis .het-ə-'rō-səs n, pl -o·ses -.sēz a marked vigor or capacity for growth that is often shown by crossbred animals or plants called also hybrid vigor
het·er·ot·ic -'rät-ik adj
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n.
hybrid vigour: the increased sturdiness, resistance to disease, etc., of individuals whose parents are of different races or species compared both with their parents and with the offspring of genetically similar parents.
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het·er·o·sis (het″ər-oґsis) [Gr. heterōsis alteration] the condition in which a first generation hybrid shows more vigor, as measured by growth, survival, or fertility, than either of the parent strains, usually a reflection of increased heterozygosity. Called also hybrid vigor.Medical dictionary. 2011.