Definition of dictionary:
1: a reference source in print or electronic form containing words usually alphabetically arranged along with information about their forms, pronunciations, functions, etymologies, meanings, and syntactic and idiomatic uses
2: a reference book listing alphabetically terms or names important to a particular subject or activity along with discussion of their meanings and applications
3: a reference book listing alphabetically the words of one language and showing their meanings or translations in another language
4: a computerized list (as of items of data or words) used for reference (as for information retrieval or word processing)