a promise that something will definitely happen or is definitely true, made especially to make someone less worried:
Despite my repeated assurances, Rob still looked very nervous.
give/seek/receive an assurance (that)
He gave an assurance that the work would be completed by Wednesday.
a feeling of calm confidence about your own abilities, or that you are right about something:
the calm assurance with which she handled the horse
'Jack will never agree to that,' he said with assurance.
3 [uncountable]BFI British English technical
insurance, especially to provide money when someone dies [= insurance American English]