A Ballista is an ancient military siege engine in the form of a crossbow. Typically it was used to hurl large bolts, and had better accuracy than a catapult at the expense of reduced range.
We chose the name "ballista" for this project because we too are attempting to accurately "hurl projectiles" at software in an attempt to expose robustness failures.
(Click on thumb-nails to see full-size gif images.)
Ballistae being used in a Siege
Pictures adapted from: The crossbow: mediaeval and modern military and sporting, its construction, history & management with a treatise on the balista and catapult of the ancients and an appendix on the catapult, balista & the turkish bow, by Sir Ralph Payne-Gallwey (1848-1916), New York : Bramhall House, 1958.
PLEASE NOTE: We don't have anything to do with siege weapon information, plans, construction, or any other related activities. We just used the word "Ballista" as a cool name for a computer software project! So please don't ask us for plans on how to build a siege weapon -- we can't help you with that.