Sour, v. i. [imp. & p. p.Soured (?); p. pr. & vb. n.Souring.] To become sour; to turn from sweet to sour; as, milk soon sours in hot weather; a kind temper sometimes sours in adversity.
They keep out melancholy from the virtuous, and hinder the hatred of vice from souring into severity. Addison.