Minie refers to the conical shaped bullet fired by the rifled musket. This projectile was developed by a Frenchman named Minie. The design allowed the bullets base to slightly expand once the powder was ignited and the bullet to grip the lands better which caused better accuracy from the spinning motion once the bullet left the barrel.
I hope this helps.
Gerald D. Hodge, Jr.
War Between the States Historian
Historian: 39th Georgia Volunteer Infantry Regiment