What do you call a cut tree that measures 16 feet long?

A tree that has been cut and measures 16 feet long is referred to as a log. The term "log" specifically describes a section of a tree trunk that has been severed from the stump and is often measured in length. Logs are commonly used for various purposes, including lumber production, firewood, and in the paper industry.

The other terms relate to different aspects of a tree's life or condition. A stump refers to the remaining part of the tree left above ground after it has been cut. The term round typically describes a log that is still circular in cross-section, but it is not used to denote the tree's length. Sawcut can refer to the method of cutting the wood but does not specifically identify the piece of wood itself in terms of size. Therefore, in this context, "log" is the accurate term for a cut tree section measuring 16 feet long.