What does Genesis 25:32 mean?

Either taking advantage of a moment of weakness on Esau's part or as an act of premeditation, Jacob has responded to his brother's request for stew by offering to trade a bowl for Esau's birthright or "firstborn rights" (Genesis 25:29–31). The birthright often entitled the firstborn to a double share of the inheritance and, perhaps, other significant privileges.

A wise answer to such a demand would have been to laugh and walk away. It would have been reasonable for Esau to assume Jacob was merely joking. It also would have been sensible not to be flippant about such an important issue. But Esau doesn't do anything remotely sensible. Either immediately, or as part of a longer, unrecorded conversation, he exaggerates his hunger to the point of claiming he is about to die.

Both brothers paint themselves in an unflattering light in this episode. Jacob has revealed his scheming nature. Now Esau reveals his recklessness. He has both discounted the value of his birthright and inflated the value of immediately satisfying his appetite. Whether he's very intentionally selling his birthright, or foolishly assuming this is all a game, it will cost him dearly.