In "Macbeth," what does Macbeth say about the witches when he learns that Birnam Wood is moving? What do his words signify? What growing...

The passage you refer to is in Act V, scene 5:

I pull in resolution; and begin
To doubt the equivocation of the fiend
That lies like truth...

Macbeth is losing heart, since he now understands the trick that has been played on him. The witches are not allowed to destroy people directly -- remember the sea-captain earlier who has offended them, and how they can torment him but not kill him: "Though his bark cannot be lost / Yet it shall be tempest-tossed" (Act I, scene 3). So, instead of lying to Macbeth, the witches give him true statements designed so that he is certain to misinterpret them. Now, when it is too late, Macbeth sees through their fraud.

If this which he avouches does appear
There is nor flying hence nor tarrying here.

He recognizes that there is now no place to run or hide, no sure protection, and no power that will assist him. He has gambled everything on the assurances of the witches, and now sees these were designed only to trick him.

I 'gin to be a-weary of the sun,
And wish the estate o' the world were now undone.--

Depressed, Macbeth looks his own death in the face, and desires vengefully that the whole world be ruined with him.

Ring the alarum bell!--Blow, wind! come, wrack!
At least we'll die with harness on our back.

Finally, Macbeth accepts that the best he can do is to die fighting. He still has a lingering faith in the prophecy that no man of woman born can kill him, but even this turns out false in the end.