Bir‧nam Wood /ˌbɜːnəm ˈwʊd $ ˌbɜːr-/
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.

[TahlilGaran] Dictionary of Contemporary English ▲