smh

The act of one moving their skull, and head for that matter, back and forth from convulsions in one's neck muscles from signals sent from one's brain, resulting in a turning of the head causing a shaking movement.  This is usually referred to as shaking my head, usually used in an act of displeasure or disagreement on something, and in some cases, anger.  Shaking my head can be condensed into a three letter acronym, SMH, s standing for shaking, m standing for my, and h standing for head.