It means Suck my dick

This is only used in text when a female is deemed unadmirable and a male would send to his friends "shaking my dick" to indicate that she is a no go.

This is also used to warn fellow males that a possible smash has an std.

SMD stands for "Suck my dick" in texting it can also stand for Sexual masochism disorder.

Short for surface mount device. An SMD is an electronic component that is attached directly to the surface of a PCB (printed circuit board). This is apposed to THT (through hole technology), where leads (little wires attached to the component) are inserted into holes in the PCB, soldered and excess lead is snipped off. SMD technology allows components to be smaller, which decreases overall size of tools and allows for more complexity.

shaking my head

Often used after smh

Smh=shaking my head, smd=shaking my dick.