1. a book or electronic resource that lists words alphabetically and gives their meanings, pronunciations, and other information
2. a reference book that gives information about a particular subject, with items arranged alphabetically

Examples

• She looked up the word in her English dictionary.
• The online dictionary provides audio pronunciations.
• Students should use a dictionary when writing essays.
• He bought a medical dictionary for his studies.
• The dictionary contains over 50,000 entries.
• I need to check the spelling in the dictionary.
• The biographical dictionary lists famous scientists.