We found 8 dictionaries that define the word fifth columnists:

General (7 matching dictionaries)

1. fifth columnists: Merriam-Webster
2. fifth columnists: Collins English Dictionary
3. fifth columnists: Vocabulary.com
4. fifth columnists: Cambridge Advanced Learner's Dictionary
5. fifth columnists: Wiktionary
6. Fifth columnists: Wikipedia, the Free Encyclopedia
7. fifth columnists: TheFreeDictionary.com

Computing (1 matching dictionary)

8. fifth columnists: Encyclopedia

(Note: See fifth_columnist as well.)

Definitions from Wiktionary (fifth columnist) ▸ noun:  someone who belongs to a group that secretly undermines another organization ▸ Also see fifth_columnist ▸ Words similar to fifth columnists ▸ Usage examples for fifth columnists ▸ Idioms related to fifth columnists ▸ Wikipedia articles (New!) ▸ Words that often appear near fifth columnists ▸ Rhymes of fifth columnists ▸ Invented words related to fifth columnists