A thick piece of tree trunk or branch, especially one cut for burning on a fire. (Cambridge Dictionary)
A log is a piece of a thick branch or of the trunk of a tree that has been cut so that it can be used for fuel or for making things. (Collins Dictionary)
A log is an official written account of what happens each day, for example on board a ship. (Collins Dictionary)
A part of the trunk or a large branch of a tree that has fallen or been cut off. (Oxford Dictionaries)
Brown log pillow.
Pacific yachting daily cruising log book.