Backplate

A backplate can be:-A piece of armour, part of a cuirass.A solid plate that supports some sort of equipment.A Steam Locomotive's Rear Boiler Plate where the steam controls are bolted.A solid plate which is part of a backpack harness for a person to carry some sort of equipment on their back.For the component of a scuba set harness, see backplate and wing.
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Noun
1. plate armor protecting the back; worn as part of a cuirass
(hypernym) armor plate, armour plate, armor plating, plate armor, plate armour
(part-holonym) cuirass

(n.)
A piece, or plate which forms the back of anything, or which covers the back; armor for the back.
  

Armour for the back. See the particular kinds of breastplate , brigandines , cuirasses and coats of plates for a more detailed description.

SCHIENALE [DI ANTICHE ARMATURE]. PIASTRA POSTERIORE