Its basicly abdominal pain. Since horses cannot vomit, this can pose a very serious problem. They can colic from a varity of different things such as stress, poor food quaility, allergy, dehyration, etc. Signs of colicing are rolling, not eating nor drinking, laying down, etc. The first thing to do when you see colic signs are call the vet, keep the horse walking, do not stop or let them lay down.