What is Macbeth referring to when she says doubt the equivocation of fiend?

The quote "Doubt the equivocation of the fiend" is actually spoken by Lady Macbeth, not Macbeth, in the play Macbeth by William Shakespeare.

In this context, Lady Macbeth is expressing her suspicion and doubt regarding the prophecies made by the witches. She is suggesting that the witches may be capable of trickery and deception and that their words should not be taken at face value. The idea of "equivocation" suggests that the witches may be using ambiguous or misleading language to manipulate Macbeth and Lady Macbeth.