Dictionary:

agraphia

  (ā-grăf'ē-ə)

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A disorder marked by loss of the ability to write.

[A–¹ + Greek graphein, to write + –IA¹.]

A form of aphasia characterized by loss of the ability to write. Also called anorthography.

The noun has one meaning:

Meaning #1: a loss of the ability to write or to express thoughts in writing because of a brain lesion
  Synonyms: anorthography, logagraphia