pĕr-ăcerbus, a, um, adj., very harsh to the taste.
I Lit.: uva peracerba gustatu, Cic. Sen. 15, 53.—
II Trop., very painful : mihi peracerbum fuit, quod, etc., Plin. Ep. 6, 5, 6.
per-acerbus adj., very harsh: uva gustatu. ...
An Elementary Latin Dictionary