We found 27 dictionaries that define the word aces:

General (14 matching dictionaries)

1. Aces, aces: Merriam-Webster
2. aces: Collins English Dictionary
3. ACES, aces: Vocabulary.com
4. Ace's, Aces, ace's, aces: Wordnik
5. aces: Cambridge Advanced Learner's Dictionary
6. ACEs, Aces, aces: Wiktionary
7. ACES: Dictionary.com
8. aces: Cambridge Essential American English Dictionary
9. ACES (buffer), ACES (computational chemistry), ACES (nutritional supplement), ACES, ACeS, Aces (Suzy Bogguss), Aces (album), Aces (song), Aces, The Aces (Jamaican group), The Aces (blues band), The Aces (indie pop band), The Aces (rock and roll band), The Aces: Wikipedia, the Free Encyclopedia
10. Aces: Online Plain Text English Dictionary
11. Aces: AllWords.com Multi-Lingual Dictionary
12. ACES: Stammtisch Beau Fleuve Acronyms
13. aces: FreeDictionary.org
14. aces: TheFreeDictionary.com

Business (3 matching dictionaries)

15. MoneyGlossary.com (No longer online)
16. aces: Legal dictionary
17. ACES (disambiguation), ACES: Financial dictionary

Computing (1 matching dictionary)

18. aces: Encyclopedia

Medicine (2 matching dictionaries)

19. ACES: Glossary of Lasik Laser Eye Surgery
20. ACES (disambiguation), ACES: Medical dictionary

Miscellaneous (3 matching dictionaries)

21. ACES: Acronym Finder
22. AbbreviationZ (No longer online)
23. aces: Idioms

Slang (2 matching dictionaries)

24. aces: Green’s Dictionary of Slang
25. A.C.E.S, Aces, aces: Urban Dictionary

Sports (2 matching dictionaries)

26. Hickok Sports Glossaries (No longer online)
27. 2060 Shadow-Slang (No longer online)

(Note: See ace as well.)

Definitions from Wiktionary (Aces) ▸ adjective:  (informal) Alternative form of ace (“excellent”) [(UK, slang) Excellent.] Similar: sail through, breeze through, 1, first-rate, whiz, crack, whizz, maven, tiptop, topnotch, more... Opposite: twos, threes, fours, fives, sixes, sevens, eights, nines, tens, jacks Types: ace of spades, ace of hearts, ace of diamonds, ace of clubs, more... Phrases: black aces, flying aces, easy aces, holding all the aces, aces out, more... Adjectives: other, german, many, top, black, american, red, few, great, several, easy Colors:     black,     red,     white,     gold,     silver, more... ▸ Words similar to aces ▸ Usage examples for aces ▸ Idioms related to aces ▸ Wikipedia articles (New!) ▸ Popular nouns described by aces ▸ Words that often appear near aces ▸ Rhymes of aces ▸ Invented words related to aces