In*form"al (?), a. [Pref. in- not + formal.]
1.
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.
2.
Deranged in mind; out of one's senses.
[Obs.]
These poor informal women.
Shak.
© Webster 1913.