Meaning: Shaking my head
“SMH” stands for “shaking my head”. Specifically, it refers to shaking one’s head left-to-right in disapproval. Although shaking one’s head is used both to say “yes” and “no”, depending on the direction, this saying is used exclusively to express disapproval. It is often used in response to something that is considered stupid, ridiculous, or otherwise worthy of expressing an almost resigned disapproval and disappointment.