keynotePronunciation: /ˈkiːnəʊt/Translate keynote | into Italian | into Spanish Definition of keynote noun 1a prevailing tone or central theme:individuality is the keynote of the Nineties [as modifier] (of a speech) setting out the central theme of a conference: he delivered the keynote address 2 Music the note on which a key is based. Derivatives keynoter noun keynote in other Oxford dictionaries Definition of keynote in the US English dictionary