Undecipherable

a. [UN-¹ 7 b and 5 b.] That cannot be deciphered or made out; indecipherable: a. Of writings, inscriptions, etc.

1758.  H. Walpole, Lett. to Mann, 23 Feb. (1846), III. 346. Your copyist or his original have made undecypherable mistakes.

a. 1827.  Miss Benger, in Literary Souvenir, 39. This paper … being in many parts almost undecypherable.

1862.  Stanley, Serm. in East (1863), 136. In another fifty years it is probable that many of them will be almost undecypherable.

1877.  ‘H. A. Page,’ De Quincey, II. xviii. 128. The rest of this letter is so mutilated as to be undecipherable.

  b.  transf.

1757.  Chesterf., Lett., in Misc. Wks. (1777), II. 435. Public matters have been long, and are still, too undecypherable for me to understand, consequently to relate.

1822–56.  De Quincey, Confess. (1862), 272. Its cause, its nature, and its undecipherable issue.

1850.  Grote, Greece, VIII. 574. In settling the undecipherable portions of the problem.

1876.  T. Hardy, Ethelberta. This deep undecipherable habit sometimes suggested … Ethelberta’s busy brain to her sisters.

  Hence Undecipherability; -ably adv.

1847.  Webster, Undecipherably.

1881.  Ruskin, Morn. Florence, 35. The whole landscape is quite undecipherally changed and spoiled.

1890.  Standard, 17 Jan., 5/3. Owing to the undecipherability of many of the signatures.