Cramps were a mild condition wherein muscles involuntarily contracted. Cramps were an unpleasant sensation and were often the result of stress or strain on the muscles in question. The muscles could also be part of an autonomous muscular system, such as the stomach.
When trying to access a secure section of San Francisco's Mercy Hospital, Doctor Leonard McCoy baffled a security guard by describing Gillian Taylor's supposed medical condition as "immediate post-prandial upper-abdominal distension", which he later described to Admiral Kirk as the scientific name for cramps. (Star Trek IV: The Voyage Home)
While on a shuttle mission with Tom Paris in 2373, investigating energy signatures, B'Elanna Torres suffered a cramp, complaining that "Klingon bodies weren't meant to sit in a cockpit for five hours at a stretch." (VOY: "The Swarm")
While on board the USS Prometheus in 2374, The Doctor told the Romulans in control of the vessel that the Terothka virus they supposedly were exposed to might give them unbearable stomach cramps, though the rash might be worse. (VOY: "Message in a Bottle")