(noun)
a saclike organ in animals in the digestive tract of a vertebrate that is located between the esophagus and duodenum and typically consists of a simple often curved sac with an outer serous covering, a strong muscular wall that contracts rhythmically, and an inner mucous membrane lining that contains gastric glands and that stores food in the process of digestion;
e.g. My stomach bloats when I have eaten a lot of food.