A device capable of registering a specific substance or physical phenomenon, and that optionally sounds an alarm or triggers a warning.
An indicator showing the depth of the water in a boiler.
A galvanometer, usually portable, for indicating the direction of a current.
A device or mechanism which is designed to protect.
A state or other subject under international law, exercising a protectorate over another subject in international law.
One having the care of the kingdom during the king's minority; a regent.
One who prevents interference.
A cardinal, from one of the more considerable Roman Catholic nations, who looks after the interests of his people at Rome; also, a cardinal who has the same relation to a college, religious order, etc.
Someone who protects or guards, by assignment or on their own initiative.