To become less happy or enthusiastic about someone or something; to begin to dislike or be repelled by someone or something, especially someone or something that had been liked or favored. I was really interested in film studies when I first got into college, but I soured on it after I started encountering the obnoxious, elitist types of people who specialize in that field. I don't know why, but John always sours on the women he dates after only a couple of weeks.