Definition of beware verb from the Oxford Advanced Learner's Dictionary

 

beware

 verb
verb
BrE BrE//ˈweə(r)//
 
; NAmE NAmE//ˈwer//
 
[intransitive, transitive]
 
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(used only in infinitives and in orders) if you tell somebody to beware, you are warning them that somebody/something is dangerous and that they should be careful beware of somebody/something Motorists have been warned to beware of icy roads. beware (of) doing something Beware of saying anything that might reveal where you live. beware somebody/something It's a great place for swimming, but beware dangerous currents. Word Origin Middle English: from the phrase be ware (from be- and archaic ware ‘aware’).
See the Oxford Advanced American Dictionary entry: beware