1. a hole in a piece of wood where a knot has fallen out or been removed

Examples

• The old wooden fence had several knotholes where the wood had decayed.
• Children used to peek through the knothole in the tree to see what was on the other side.
• The carpenter filled the knotholes with wooden plugs before staining the board.
• Rain leaked through the knotholes in the barn's wooden roof.
• A small bird nested inside the knothole of the ancient oak tree.