Alpha-glucosidase inhibitor: A class of oral medications for type 2 diabetes that decrease the absorption of carbohydrates from the intestine, resulting in a slower and lower rise in blood glucose throughout the day, especially right after meals. Before carbohydrates are absorbed from food, they must be broken down into smaller sugar particles like glucose by enzymes in the small intestine. One of the enzymes involved in breaking down carbohydrates is called alpha glucosidase. By inhibiting this enzyme, carbohydrates are not broken down as efficiently and glucose absorption is delayed. The alpha-glucosidase inhibitors include Precose (acarbose) and Glyset (miglitol).