We found 23 dictionaries that define the word thingamajig:

General (19 matching dictionaries)

1. thingamajig: Longman Dictionary of Contemporary English
2. thingamajig: Merriam-Webster
3. thingamajig: Oxford Learner's Dictionaries
4. thingamajig: American Heritage Dictionary of the English Language
5. thingamajig: Collins English Dictionary
6. thingamajig: Vocabulary.com
7. thingamajig: Wordnik
8. thingamajig: Cambridge Advanced Learner's Dictionary
9. thingamajig: Wiktionary
10. thingamajig: Webster's New World College Dictionary, 4th Ed.
11. thingamajig (thingumajig): The Wordsmyth English Dictionary-Thesaurus
12. thingamajig: Infoplease Dictionary
13. thingamajig: Dictionary.com
14. thingamajig: Cambridge Essential American English Dictionary
15. Thingamajig: Wikipedia, the Free Encyclopedia
16. thingamajig: Rhymezone
17. thingamajig: FreeDictionary.org
18. thingamajig: Mnemonic Dictionary
19. thingamajig: TheFreeDictionary.com

Business (1 matching dictionary)

20. Construction Term Glossary (No longer online)

Computing (1 matching dictionary)

21. thingamajig: Encyclopedia

Slang (2 matching dictionaries)

22. thingamajig: Green’s Dictionary of Slang
23. thingamajig: Urban Dictionary

(Note: See thingamajigs as well.)

Definitions from Wiktionary (thingamajig) ▸ noun:  (informal) Something that one does not know the name of. Similar: thingamabob, thingumabob, thingmajig, doodad, dojigger, thingmabob, thingummy, dohickey, thingumajig, doohickey, more... Types: gadget, gizmo, contraption, apparatus, device, instrument, more... ▸ Words similar to thingamajig ▸ Usage examples for thingamajig ▸ Idioms related to thingamajig ▸ Wikipedia articles (New!) ▸ Popular adjectives describing thingamajig ▸ Words that often appear near thingamajig ▸ Rhymes of thingamajig ▸ Invented words related to thingamajig