- http://dictionary.cambridge.org
- http://dictionary.reference.com
- http://afen.onelook.com
- http://www.merriam-webster.com
- http://www.thefreedictionary.com
- http://www.ldoceonline.com
- https://www.allwords.com
- http://www.collinsdictionary.com
- http://www.macmillandictionary.com
- http://ahdictionary.com
- https://www.wordnik.com
