Yup, I think it's indigestion too - literally meaning "not-digesting" - it can be caused by over eating, drinking or gastroparesis (slow-digestion). http://www.nlm.nih.gov/medlineplus/ency/article/003260.htm
A food intolerance (not food allergy) is when some type of food irritates a person’s digestive system or when the gut is unable to break down that particular food stuff.
IBS is a general term for abnormal intestinal contractions/spasms that could be triggered by a variety of causes. They do say anyone with IBS should try a lactose free diet (food intolerance to dairy) http://www.nlm.nih.gov/medlineplus/ency/article/000246.htm