Definition of Forma non observata, infertur adnullatio actus
Where form is not observed, a nullity of the act is inferred. Where the law prescribes a form, the non-observance of it is fatal to the proceeding, and the whole becomes a nullity.
That's the definition of Forma non observata, infertur adnullatio actus in Black's Law Dictionary 6th Edition. Courtesy of Cekhukum.com.