Which reference would best explain what an author means when she uses the adjective saturnine I describe a character?

An English dictionary, such as the Oxford English Dictionary or Merriam-Webster's Collegiate Dictionary, would best explain what an author means when she uses the adjective "saturnine" to describe a character. These dictionaries provide detailed definitions and examples of usage for the word, which can help the reader understand how the author intended it to affect the characterization.