scutum

noun

• An oblong shield made of boards or wickerwork covered with leather, with sometimes an iron rim; carried chiefly by the heavy-armed infantry of the Roman army.
• A scute.
• A shield-like protection, such as the scutum protecting the back of a hard tick (cf. alloscutum, conscutum)
• One of the two lower valves of the operculum of a barnacle.
• The kneecap.