To beshrew is to invoke a curse on someone. Horrified at discovering an empty baking pan, you might yell, "Beshrew all of you who ate my brownies!"
The verb beshrew is so old fashioned that you're most likely to discover it in a play or poem by Shakespeare, who used it frequently. When the Nurse in Romeo and Juliet says, "Beshrew your heart for sending me about, to catch my death with jaunting up and down!", what she means is "Curse you for making me run around so much!" Beshrew comes from shrew, an animal believed to have a poisonous bite.