Controller

Part of speech: noun (n.)

1. One who, or that which, controls or restraines; one who has power or authority to regulate or control; one who governs. The great controller of our fate Deigned to be man, and lived in low estate. Dryden.

2. An officer appointed to keep a counter register of accounts, or to examine, rectify, or verify accounts. [More commonly written controller.]

3. An iron block, usually bolted to a ship's deck, for controlling the running out of a chain cable. The links of the cable tend to drop into hollows in the block, and thus hold fast until disengaged.