noun

• (nautical) A floating device, usually of wood, used in navigation to estimate the speed of a vessel through water.
  "1659, Navigation by the Mariners Plain Scale New Plain'd, by John Collins Every Noon the Master and his Mates take the reckoning off the Log-board, and double the Knots run, and then divide the Product, which is the number of Miles run by three, the quotient is the Leagues run since the former Noon, and according to custom the Log is thrown every two hours, and I never knew the course nearer expressed on the Log-board, then to half a point of the Compass."
• (figuratively) A blockhead; a very stupid person.
• (surfing slang) A heavy longboard.
  "1999, Neal Miyake https://web.archive.org/web/20060530122555/http://www.iav.com/~sponge/sesh/new2/sesh213.htm I know he hadn’t surfed on a log much in his childhood"
• (figuratively) A rolled cake with filling.

verb

• (transitive) To cut trees into logs.
• (transitive) To cut down (trees).
  "Since the mid-1980s, when Indonesia first began to clear its bountiful forests on an industrial scale in favour of lucrative palm-oil plantations, “haze” has become an almost annual occurrence in South-East Asia. The cheapest way to clear logged woodland is to burn it, producing an acrid cloud of foul white smoke that, carried by the wind, can cover hundreds, or even thousands, of square miles."
• (intransitive) To cut down trees in an area, harvesting and transporting the logs as wood.

noun

• (computer science) Specifically, an append-only sequential record of events written to a file, display, or other data stream.

verb

• (transitive) To make, to add an entry (or more) in a log or logbook.
  "to log the miles travelled by a ship"
• (transitive) To travel (a distance) as shown in a logbook.
• (transitive) To travel at a specified speed, as ascertained by a chip log.