(as) deaf as a post informal
This idiom is likely offensive to others.
Her grandfather's as deaf as a post.
My grandma can't hear you even if you shout; she's deaf as a post.
After years of listening to very loud music, now Linda is deaf as a post.
To act recklessly; to have a desire for death
Secrets cannot be revealed by the dead.
Completely lifeless or defunct.
"(as) deaf as a post" is also "deaf as an adder". The first idiom has its origin in John Palsgrave's Acolastus (1540).
To do domething based on your emotions rather than for rational reasons
I can't believe that Tom beat his classmate. He's always the one who let his heart rule his head.