Final answer:
The answer cannot be given without a specific reference to 'Charlotte's Web' by E.B. White, which is not provided in the excerpts.
Step-by-step explanation:
The student's question, "What does Charlotte tell Wilbur that the word 'gullible' means?" does not directly relate to any provided quotes, and therefore cannot be answered through the excerpts given. In terms of the novel's content, the word 'gullible' could be discussed in terms of character interactions or vocabulary lessons, but it requires a specific reference to the text of 'Charlotte's Web' by E.B. White, which is not included among the provided information.