The term 'uncontrolled jerk' can be summarized as a sudden, unexpected movement or SPASM. The crossword solution for this term is SPASM, which is an involuntary contraction of a muscle or group of muscles. This type of movement can be caused by a variety of factors, including medical conditions, physical trauma, or even emotional stress. It is important to note that uncontrolled jerks are not the same as voluntary movements, and can be quite disruptive and uncomfortable.