| any of various devices for determining the speed of a ship by means of a vaned rotor streamed at the end of a log line upon which it exerts a torsion transmitted to a registering device on board. |
| patent log n. Nautical A torpedo-shaped instrument with rotary fins that is dragged from the stern of a vessel to measure the speed or distance traveled. Also called screw log, taffrail log. |
| screw log n. See patent log. |
