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Webster 1913 Edition

Verb.

[1st pref.

un-

deaf

To free from deafness; to cause to hear.

[Obs.]

Shak.

Verb.

To free from deafness. [Not in use.]

undeaf ‎(third-person singular simple present undeafs, present participle undeafing, simple past and past participle undeafed)

(transitive, nonce word) To free from deafness.
- Shakespeare
  My death's sad tale may yet undeaf his ear.