BEWARE

v. (only in imper. or infin.) 1 intr. (often foll. by of, or that, lest, etc. + clause) be cautious, take heed (beware of the dog; told us to beware; beware that you don't fall). 2 tr. be cautious of (beware the Ides of March).

[ BE + WARE(3) ]