Someone whom one has befriended, taken care of, or treated well but proves to be traitorous, untrustworthy, deceitful, or ungrateful. (A less common variant of "a viper in one's bosom." Used especially in the phrase "nourish/nurse/nurture a serpent in one's bosom.") Well, it turns out that Margaret was quite a serpent in my bosom. I put my neck on the line to get her a job in our company, and then she turns around and tries to get me fired! I thought our love was not only mutual but indestructible; and yet, I have nursed a serpent in my bosom all these years: my darling husband has cast me out and run off with a younger woman.

To befriend, look after, or take care of someone who proves to be traitorous, untrustworthy, deceitful, or ungrateful. (A less common variant of "nurse a viper in one's bosom.") I thought the profligate had seen the light and was seeking redemption, and so I took him into my care. But before long, I knew I had nursed a serpent in my bosom, as I awoke one morning to find myself robbed blind! I thought our love was not only mutual but indestructible; and yet, I have nursed a serpent in my bosom all these years: my darling husband has cast me out and run off with a younger woman.

To befriend, look after, or take care of someone who proves to be traitorous, untrustworthy, deceitful, or ungrateful. (A less common variant of "nurture a viper in one's bosom.") I thought the profligate had seen the light and was seeking redemption, and so I took him into my care. But before long, I knew I had nurtured a serpent in my bosom, as I awoke one morning to find myself robbed blind! I thought our love was not only mutual but indestructible; and yet, I have nurtured a serpent in my bosom all these years: my darling husband has cast me out and run off with a younger woman.

To befriend, look after, or take care of someone who proves to be traitorous, untrustworthy, deceitful, or ungrateful. (A less common variant of "nourish a viper in one's bosom.") I thought the profligate had seen the light and was seeking redemption, and so I took him into my care. But before long, I knew I had nourished a serpent in my bosom, as I awoke one morning to find myself robbed blind! I thought our love was not only mutual but indestructible; and yet, I have nourished a serpent in my bosom all these years: my darling husband has cast me out, having run off with a younger woman.

An unhelpful or otherwise disagreeable bureaucrat. A humorous play on the phrase "civil servant"; serpents are typically depicted as evil or villainous. I can't deal with any more civil serpents—they just keep sending me from office to office.