~ (of sb/sth / of doing sth) (used only in infinitives and in orders) if you tell sb to beware, you are warning them that sb/sth is dangerous and that they should be careful:
[V] Motorists have been warned to beware of icy roads. * Beware of saying anything that might reveal where you live. * [VN] It's a great place for swimming, but beware dangerous currents. [also V-ing]
