- The definition of beware is to be cautious of and alert to potential dangers or risks.
If you need to be cautious of hitting a deer when driving on a dark road, this is an example of when you need tobeware of deer.
Beware of deer crossing this road.Licensed from iStockPhoto
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verb be·wared, be·war·ing, be·wares verb, transitive
Origin: Middle English ben war : ben, to be; see be + war, on one's guard; see ware2.