9 letters · 12 points in Scrabble
adjective based on custom rather than documentation; ; - J.L.T.C.Spence
adjective using speech rather than writing
adjective said or done without having been planned or written in advance
originFrom Middle English unwriten, from Old English unwriten, unġewriten (“unwritten”), equivalent to un- + written.
Etymology from Wiktionary, CC BY-SA 3.0