It means that you are full and can't eat anymore.
"Stuffed to the gills" means when you are really full and can't eat anything else. Hope this helped. I know how hard it is with idioms!
The idiom "stuffed to the gills" means to be completely full, especially after eating. It originates from the idea of fish gills filled with food, representing no additional room for more. The phrase can be used in various contexts to convey satisfaction after a large meal.
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