UNWRITTEN

spontaneous, ad-lib, unwritten

(adjective) said or done without having been planned or written in advance; “he made a few ad-lib remarks”

oral, unwritten

(adjective) using speech rather than writing; “an oral tradition”; “an oral agreement”

unwritten

(adjective) based on custom rather than documentation; “an unwritten law”; “rites...so ancient that they well might have had their unwritten origins in Aurignacian times”- J.L.T.C.Spence

Source: WordNet® 3.1

Etymology

Adjective

unwritten (not comparable)

Not written.

Oral or otherwise communicated without writing.

Implicit or understood but not formally articulated.

Containing no writing; blank.

Verb

unwritten

past participle of unwrite

Source: Wiktionary

Un*writ"ten, a.

1. Not written; not reduced to writing; oral; as, unwritten agreements.

2. Containing no writing; blank; as, unwritten paper. Unwritten doctrines (Theol.), such doctrines as have been handed down by word of mouth; oral or traditional doctrines.

– Unwritten law. Etym: [Cf. L. lex non scripta.] That part of the law of England and of the United States which is not derived from express legislative enactment, or at least from any enactment now extant and in force as such. This law is now generally contained in the reports of judicial decisions. See Common law, under Common.

– Unwritten laws, such laws as have been handed down by tradition or in song. Such were the laws of the early nations of Europe.