beware Definition

beware
verb

intr
1a. To be careful of it; to be on one's guard;

Example: Beware of the dog
Form: beware of something (usually)
intr
1b. rather formal or literary
(with the subjunctive) to take care that one does, or does not, do something.
Example: should beware lest he fall
Form: beware that something (usually)
Form: beware lest something
2. old use or literary
To be on one's guard against something or someone.
Example: Beware the cruel hand of fate

Etymology: 13c: from be (imperative) + ware cautious or wary.