Abdominal muscle spasm, also known as abdominal rigidity, is a powerful, involuntary contraction of the muscles of the abdomen.During a spasm, the muscle will feel stiff and tender if you apply pressure.ike any other muscles in the body, your abdominal muscles can have spasms that occur as a result of muscle strain during heavy use or overuse, fatigue, dehydration, and alcohol or drug use.