- (a.) Not in the regular, usual or established form; not according to official, conventional, prescribed or customary forms or rules; irregular; hence, without ceremony; as, an informal writting, proceeding or visit.
- (a.) Deranged in mind; out of one's senses.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). informal. Retrieved September 24, 2026, from http://smartdefine.org/informal/definitions/2021490 |
| Chicago | Webster's. 2011. "informal" http://smartdefine.org/informal/definitions/2021490 (accessed September 24, 2026). |
| Harvard | Webster's 2011, informal, Smart Define, viewed 24 September, 2026, <http://smartdefine.org/informal/definitions/2021490>. |
| MLA | Webster's. "informal" 27 May 2011. Web. 24 September 2026. <http://smartdefine.org/informal/definitions/2021490> |