Bir ‧ nam Wood /ˌbɜːnəm ˈwʊd $ ˌbɜːr-/ BrE AmE
the wood near Birnam in Perthshire, Scotland. In Shakespeare's play Macbeth , Macbeth is told that he will only be defeated when Birnam Wood comes to Dunsinane. Later, his enemy's army comes through Birnam Wood and each soldier cuts a large branch to hide himself, so that when the army moves on it looks as if the wood is moving. Macbeth is defeated and killed.