Twist (lumber defect)
A lumber defect where the board warps so the four corners no longer lie in the same plane, creating a propeller-like distortion caused by irregular grain and uneven drying.
In-Depth Explanation
Twist is one of the most problematic forms of warp because it affects the board in multiple dimensions simultaneously, making it difficult to correct with standard flattening techniques. A twisted board rocks diagonally when placed on a flat surface, with two opposite corners lifted. Spiral grain in the original tree is a primary cause, as the wood fibers dry and shrink unevenly along their twisted path. Improper stickering, uneven airflow during drying, and moisture content variations can also contribute to twist. Mild twist can sometimes be planed out if the board is thick enough, but severe twist often means the lumber must be cut into shorter pieces.
Usage Example
I sighted down the 2x6 and could clearly see it was twisted so I put it back and picked a straighter one.