amnesia

‖n. [ NL., fr. Gr. 'amnhsi`a; 'a priv. + mna^sqai to remember. ] 1. (Med.) Forgetfulness; loss of long-term memory. Quian. [ 1913 Webster + AS ]

2. (Med.) A defect of speech, from cerebral disease, in which the patient substitutes wrong words or names in the place of those he wishes to employ. [ Obs. ] Quian. [ 1913 Webster + AS ]

adj. def>Having lost memories, especially due to brain injury or mental shock; suffering from amnesia.
Syn. -- amnesic [ WordNet 1.5 ]