What is a stomach spasm?

There is no such thi: I do not know what you mean. Are you having stomach ache? In case you are having persistent pain in your belly(more than one week), you should go see your doctor for further evaluation.

Many possibilities.: Peptic ulcers, constipation, gallbladder disease, hepatitis, colitis, diverticulitis, incarcerated hernia, intussusception, bowel obstruction, bladder infection...these are just a partial list of possible causes of "stomach spasm". What this tells us is that it's best to seek a doctor's exam before trying to make a diagnosis.