Equivocation: A statement that is not literally false, but is designed to mislead. Macbeth is led to his destruction by the equivocation of the witches, particularly as it is demonstrated through the appearance of the three apparitions in Act IV, scene i. Macbeth is told to "Beward Macduff!" Then he is told that "none of woman born" can harm him. Finally, he is given this reassurance:
Macbeth shall never vanquished be until
Great Birnam Wood to high Dunsinane Hill
Shall come against him.
The statements prove to be true, literally, as final events in the drama unfold, but they mislead Macbeth, as intended, into a false sense of invulnerability. As a result, he continues in his wicked ways and is beheaded by Macduff.
Before his death, Macbeth realizes the witches have equivocated. Macduff's mother had not born him naturally at his birth, and Birnam Wood does move up the hill, as soldiers cut down boughs to shield themselves in their attack. Ironically, by feeling safe, Macbeth is set upon a straight path to his destruction. Further irony can be found in this; in one of the three prophecies, the witches did not equivocate, but Macbeth did not recognize the truth when it was presented to him. "Beware Macduff!" was not misleading at all.