From The Collaborative International Dictionary of English v.0.48 [gcide]:
Grapeshot \Grape"shot`\, n. (Mil.)
A cluster, usually nine in number, of small iron balls, put
together by means of cast-iron circular plates at top and
bottom, with two rings, and a central connecting rod, in
order to be used as a charge for a cannon. Formerly grapeshot
were inclosed in canvas bags.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
grapeshot
n 1: a cluster of small projectiles fired together from a cannon
to produce a hail of shot [syn: grapeshot, grape]