An irony is an image or speech or action which actually means oppositie to its surface meaning. There are several ironies in Macbeth.
i)Duncan’s speech regarding the the thane of Cawdor: “there is not art to find the mind’s construction on the face.” Duncan could never imagine that this will be true for Macbeth, whom he trust the most.
ii)During the second meeting with the witches ,the apparition of the bloody child says to Macbeth “None of woman born shall harm Macbeth” Macbeth became over confident at this prophesy, but he could never imagine that Macduff was born by a cesarean section , and therefore will kill him.
iii) During the second meeting with the witches ,the apparition of the crowned child says to Macbeth “Macbeth will not die until Birnam wood will come near Dunsinane Hill” This prophesy is a irony for Macbeth because he thinks it will never happen but in reality it happens.