Horripilant is an unusual and seldom used word that describes a feeling of fear or terror which causes goosebumps or hair to stand on end. There are several different synonyms for horripilant that can be used to convey this same meaning, including eerie, spine-tingling, chilling, creepy, unsettling, unnerving and hair-raising. These words all convey a sense of unease or discomfort, which causes a physical reaction in the body. They are particularly useful when describing situations or emotions that are difficult to explain using everyday language. If you want to describe something that invokes a sense of fear or terror, using one of these synonyms is a good way to do so.