[bә'listә]
n.
发射石块的古代武器

[ noun ]
an engine that provided medieval artillery used during sieges; a heavy war engine for hurling large stones and other missiles
<noun.artifact>

Ballista \Bal*lis"ta\, n.; pl. {Ballist[ae]}. [L. ballista,
balista, fr. Gr. ba`llein to throw.]
An ancient military engine, in the form of a crossbow, used
for hurling large missiles.