If someone is corpulent, they are fat — usually quite a lot, and often in a round, heavy way. Writers like this word because it sounds more mannered than “fat.” You will find it in novels and in older news, often about a middle-aged or older man with a big belly. In the street, almost nobody says “He’s corpulent.” They say “He’s fat” or “He’s overweight.” The word is not a compliment, but it is less of a slap than “fat.” It can even sound faintly comic, like a label from an old novel. Though actually, it still means the same simple thing: a body carrying a lot of fat. The fancy sound does not make it kinder; it only makes it more bookish.

肥胖的、大腹便便的（偏書面；口語多說胖、過重）