host has 7 distinct synonyms spread across 5 of its 11 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is parasite.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
Synonyms, antonyms and the broader and narrower relations for host come from Princeton University’s WordNet. Full sources and licences.
an animal or plant that nourishes and supports a parasite; it does not benefit and is often harmed by the association
a person who acts as host at formal occasions (makes an introductory speech and introduces other speakers)
any organization that provides resources and facilities for a function or event
“Atlanta was chosen to be host for the Olympic Games”
(medicine) recipient of transplanted tissue or organ from a donor
a technical name for the bread used in the service of Mass or Holy Communion
be the host of or for
“We hosted 4 couples last night”