'Improperia' definitions:

Definition of 'Improperia'

From: GCIDE

Improperia \Im`pro*pe"ri*a\, n. pl. [L., reproaches.] (Mus.) A series of antiphons and responses, expressing the sorrowful remonstrance of our Lord with his people; -- sung on the morning of the Good Friday in place of the usual daily Mass of the Roman ritual. --Grove. [1913 Webster]