Balistraria, also known as an arrow-slit or crosslet, refers to a small vertical opening in a fortification wall through which arrows or crossbows could be fired. Though this term is slightly obscure, there are various synonyms for it, including "loophole," "embrasure," and "slit." These words all refer to a small opening in a wall that was designed for the purpose of defense or warfare. Other related words include "murder hole," "portcullis," "rampart," and "bastion." Each of these words may be used to describe different aspects or features of a fortification or castle. Overall, these synonyms help to convey a sense of the historical and military significance of balistrarias and fortifications.