bowman, or crossbowman
Latin, arbalistarius, balistarius.
Early volumes of the Phillimore edition translated these terms as gunner; this edition standardises on bowman, generally preferred by later editors. A bowman might be in charge of a throwing engine or, more probably, he would be a crossbowman.
The crossbow was probably unknown in Anglo-Saxon England. It has been doubted whether crossbowmen were part of the Norman army in 1066. The chronicle sources are silent or ambiguous, and there are doubts about the authenticity of the one source which does mention them, the Carmen de hastingae proelio. It takes the eye of faith to detect a crossbowman on the Bayeux Tapestry. There is no doubt at all, however, that crossbowmen were recorded in Domesday Book, which would seem to tip the balance of argument in favour of their use by the Conqueror at Hastings. Balistarius may be ambiguous, but arbalistarius can only refer to a crossbowman, and even the apparent references to simple archers probably conceals crossbowmen too.
All the bowmen recorded in Domesday Book were of continental origin. Most were tenants-in-chief or royal sergeants, three - Nicholas, Godbold and Odo - holding modestly substantial estates of baronial proportions.
For further information, see Jim Bradbury, The medieval archer (1985); and Matthew Strickland, 'Military technology and conquest: the anomaly of Anglo-Saxon England', Anglo-Norman Studies, vol. 19 (1997), pages 353-82.