imaginary switch on a baby's back that makes it cry when put down
Jocular term used among parents to describe the phenomenon where a baby who seems sound asleep starts crying the moment they are laid in bed, as if a switch on their back is activated.
Just when I thought the baby had finally fallen asleep and laid them on the futon, the back switch flipped and they started crying.
My baby has a sensitive back switch and wakes up the moment I put them down.
A humorous compound of 背中 (back) and スイッチ (switch), coined by Japanese parents to describe the common infant behavior of waking and crying upon being placed on their back.