What is Challenge Propter Affectum?

Legal Definition
A challenge interposed on account of an ascertained or suspected bias or partiality, and which may be either a principal challenge or a challenge to the favor. Harrisburg Bank v. Forster, 8 Watts (Pa.) 306 ; State v. Sawtelle, 66 N. H. 488, 32 Atl. 831; Jewell v. Jewell, 84 Me. 304, 24 Atl. 858, 18 L. R. A. 473.
-- Black's Law Dictionary
Legal Definition
An objection to a juror because of bias.
-- Ballentine's Law Dictionary