What do you call a place in timber where a bump or knot has fallen out?

The correct term for a place in timber where a bump or knot has fallen out is referred to as a knothole. In woodworking and lumber selection, a knothole is specifically recognized as the resulting hole left after the removal of a knot, which is a natural feature in wood that can affect both the appearance and strength of the material.

Understanding the term knothole is critical in the context of timber quality and application, as these defects can impact the structural integrity depending on their size and location within the piece. The presence of knotholes is often cited in lumber grading, as they can create weaknesses in the wood.

The other options, while related to timber and its characteristics, do not accurately describe the specific phenomenon of a knot falling out. A defect generally denotes any flaw in the wood that might include splits, checks, rot, or other undesirable characteristics. A void commonly refers to any empty space or opening not necessarily associated with a knot, while inclusion typically refers to a characteristic or material that is embedded in the wood, which does not specifically address the situation of a knot falling out.