1. (

• unwritten

) 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 ;

2. (

• oral ,
• unwritten

) using speech rather than writing; "an oral tradition"; "an oral agreement" ;

3. (

• ad-lib ,
• spontaneous ,
• unwritten

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