Ka·tha·rev·u·sa 
(kä′thä-rĕv-sä′)
(kä′thä-rĕv-sä′)n.
The puristic, archaizing form of Modern Greek, having morphological and lexical features borrowed from Koine.
[Modern Greek kathareuousa, from Greek, feminine present participle of kathareuein, to be pure, from katharos, pure.]