To find synonyms for a word, you can use online resources like Dictionary.com, Thesaurus.com, or Answers.com. These websites provide tools that allow you to enter a word and find its synonyms. You can simply type in the word "ghastly" and search for its synonyms. In this case, "horrible" can be considered synonyms for "ghastly". It's always a good practice to use multiple sources to ensure accuracy and find the most appropriate synonyms for a particular context.