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intermediate host[‚in·tər′mēd·ē·ət ′hōst]
(in biology). (1) An animal in which sexually immature parasites live. Those animals in which parasites reach sexual maturity and reproduce are called definitive hosts. Man, for instance, is the intermediate host of the causative agent of malaria (malarial plasmodium), while the mosquito is the definitive host.
(2) A plant on which a rust fungus, or a parasite of a cultivated plant, passes part of its life cycle. Most of these fungi form aecidial sporangiophores, or aecidia, on intermediate hosts; for example, stem rust of the grasses Puccinia graminis forms on barberry leaves.