Any apparatus for measuring the speed of a ship; also the daily record of events on board a ship or aircraft.
The log originally consisted of a piece of weighted wood attached to a line with knots at equal intervals that was cast from the rear of a ship. The vessel's speed was estimated by timing the passage of the knots with a sandglass (like an egg timer). Today logs use electromagnetism and sonar.
1. A segment of the trunk of a tree when stripped of branches.
2. A written record of events on a voyage (of a ship or plane).
3. A written record or journal of events or transactions
4. A float that trails from a ship by a knotted line in order to measure the ship's speed through the water.

ETYM (USA).
1. To cut lumber, as in woods and forests; SYN. lumber.
2. To enter into a log, as on ships and planes.

In mathematics, abbreviation for logarithm.

A record of transactions or activities that take place on a computer system. See logarithm.