The antonym for ‘gaunt’ is ‘plump’.
‘Gaunt’ describes something that is very thin and bony, often due to lack of food, illness, or extreme conditions. On the other hand, ‘plump’ refers to something that is well-filled out, stout, or somewhat rounded, usually suggesting a healthy or robust appearance. Using these words in contrast highlights differences in physical condition and can convey a variety of meanings in descriptive writing.