Source : Webster's Revised Unabridged Dictionary (1913)

Torpedo shell \Torpedo shell\ (Ordnance)
   A shell longer than a deck-piercing shell, with thinner walls
   and a larger cavity for the bursting charge, which consists
   of about 130 pounds of high explosive. It has no soft cap,
   and is intended to effect its damage by the powerful
   explosion which follows on slight resistance. It is used
   chiefly in 12-inch mortars.