Spasm/ˈspæzəm/ Definition 1 of 3Pro Tip 1/3Involuntary Movement Indicates an uncontrollable muscle action, not done on purpose. She felt a sudden spasm in her eyelid while trying to concentrate. Pro Tip 2/3Often Painful Muscle spasms are usually uncomfortable or painful, causing visible or subtle movements. After the long run, he was troubled by a spasm in his thigh. Pro Tip 3/3Medical Context Usually used in medical or health-related discussions to describe symptoms. The patient reported back spasms after lifting heavy objects.