host /hōst/ [L, hospes] , 1. an organism in which another, usually parasitic, organism is nourished and harbored. A definitive host is one in which the adult parasite lives and reproduces. An intermediate host is one in which the parasite exists in its nonsexual, larval stage. A reservoir host is a primary animal host for organisms that are sometimes parasitic in humans and through which humans may become infected. 2. the recipient of a transplanted organ or tissue. Compare donor.
