Emily Dickinson Lexicon

SOUR, v.i.

1. To become acid; to acquire the quality of tartness or pungency to the taste. Cider sours rapidly in the rays of the sun. When food sours in the stomach, it is evidence of imperfect digestion.
2. To become peevish or crabbed. They hinder the hatred of vice from souring into severity. – Addison.