the act of causing something to move up and down (or back and forth) with quick movements
"The toddler was shaking the rattle vigorously, making it dance in his hand."
A movement that shakes.
"The shaking of his hands made it impossible to hold a steady cup."
present participle of shake
"The shaking leaves rattled against the branches as the wind howled outside."
In plain English: To shake means to move your body back and forth quickly, usually because you are nervous or trying to get something loose.
"He was shaking his head in disagreement when I suggested we go to the movies."