deaf as an adder
Unable to hear anything. The deafness of an adder is referred to in the Bible. A: "I'm shouting, and he's ignoring me!" B: "Oh, he's deaf as an adder! Write down whatever you're trying to communicate to him." What are you, deaf as an adder? You hear me calling you for dinner, so get in here!
deaf as an adder (or a post)
completely or extremely deaf. The traditional deafness of an adder is based on an image in Psalm 58:4: ‘the deaf adder that stoppeth her ear’.