(verb) (defective) To use caution, pay attention to (used both with and without of).
"I say, beware of all enterprises that require new clothes, and not rather a new wearer of clothes."
"Beware of false knowledge; it is more dangerous than ignorance."
"Beware the barrenness of a busy life."
"Cherish those who seek the truth but beware of those who find it."
"Beware of little expenses; a small leak will sink a great ship."
"The first step of healing is to beware of your own negative thoughts."