an·ti·dote ˈan(t)iˌdōt/ noun 1. a medicine taken or given to counteract a particular poison. synonyms: antitoxin, antiserum, antivenin "the antidote to this poison" something that counteracts or neutralizes an unpleasant feeling or a substance that cancels or opposes the effect of a remedy. And to Niall, Harry was his perfect Antidote.