The term 'uncontrollable jerks' can be summarized by the crossword solution 'spasms, ' which is a six-letter word. Spasms are involuntary muscle contractions that can cause sudden and sometimes painful movements of the body. They can be caused by a variety of medical conditions, including neurological disorders, muscle fatigue, and electrolyte imbalances. In some cases, spasms can be a sign of an underlying medical condition that needs to be addressed.