The O.E.D. or Oxford English Dictionary is a reference book that includes definitions and origins of English words, along with their different meanings. If you're looking for synonyms for O.E.D., here are some options that can be used interchangeably: 1. English dictionary 2. Lexicon 3. Wordbook 4. Vocabulary guide 5. Thesaurus 6. Glossary 7. Reference book 8. Dictionary of English 9. Word reference 10. Language guide No matter which synonym you use, these books can be of great help when it comes to understanding the meaning and proper usage of words in the English language.