Definition of ensure

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en·sure    (n-shr) KEY 

TRANSITIVE VERB:
en·sured, en·sur·ing, en·sures

To make sure or certain; insure: Our precautions ensured our safety. See Usage Note at assure.

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ETYMOLOGY:
Middle English ensuren, from Anglo-Norman enseurer : Old French en-, causative pref. ; see en-¹ + Old French seur, secure, variant of sur ; see sure