Mare’s nest is a noun that refers to a hoax or an illusion. Our word of the day combines two very familiar English words, ‘mare’ and ‘nest.’ Those conversant with the behavior of horses may know that mares don’t actually make nests. The phrase’s origin comes from that fact. A mare with a nest would be a strange hoax or something puzzling. The mall parking lot can be a mare’s nest. Just when you think you’ve found your exit, you realize it’s just a cruel hoax played by the mall’s designer.