1. Host is an organism on or in which other organism lives.
2. A host computer comprises the central hardware and software resources of a computer complex; e.g., CPU, memory, channels, disk and magnetic tape I0 subsystems plus operating and applications software. The term is used to denote all non-network items.
3. A host is an organism in which a parasite lives and by which it is nourished.
(Source: Centers for Disease Control and Prevention)