We found 17 dictionaries that define the word mentally ill:

General (12 matching dictionaries)

1. mentally ill: Longman Dictionary of Contemporary English
2. mentally ill: Merriam-Webster
3. mentally ill: American Heritage Dictionary of the English Language
4. mentally ill: Vocabulary.com
5. mentally-ill: Wordnik
6. mentally ill: Wiktionary
7. mentally ill: Dictionary.com
8. Mentally ill, The Mentally Ill: Wikipedia, the Free Encyclopedia
9. mentally ill: Rhymezone
10. mentally ill: FreeDictionary.org
11. mentally ill: Mnemonic Dictionary
12. mentally ill: TheFreeDictionary.com

Business (1 matching dictionary)

13. mentally ill: Legal dictionary

Computing (1 matching dictionary)

14. Mentally-ill, mentally ill: Encyclopedia

Medicine (2 matching dictionaries)

15. mentally ill: Merriam-Webster Medical Dictionary
16. Mentally-ill, mentally ill: Medical dictionary

Slang (1 matching dictionary)

17. mentally ill: Urban Dictionary

Definitions from Wiktionary (mentally ill) ▸ adjective:  Having a psychological disorder. Similar: insane, unsound, unstable, psychopathogenic, unhealthy, eating-disordered, clinically depressed, learning-disabled, depressed, pseudodemented, more... Opposite: sane, rational, lucid, clearheaded Types: schizophrenic, bipolar, depressive, manic, neurotic, psychotic, more... Phrases: guilty but mentally ill, national alliance for the mentally ill, Artistry of the Mentally Ill, mentally ill people, mentally ill shut in, more... ▸ Words similar to mentally ill ▸ Usage examples for mentally ill ▸ Idioms related to mentally ill ▸ Wikipedia articles (New!) ▸ Popular nouns described by mentally ill ▸ Words that often appear near mentally ill ▸ Rhymes of mentally ill ▸ Invented words related to mentally ill