be·ware (bĭ-wâr') v.
be·wared, be·war·ing, be·wares
v.
tr. To be on guard against; be cautious of: "Beware the ides of March"(Shakespeare). v.
intr. To be cautious; exert caution: We had to beware of the icy patches on the road. Beware of the dog.
[Middle English ben war : ben, to be; see be + war, on one's guard; see ware2.]