gnarl Noun a knot in wood; a large or hard knot, or a protuberance with twisted grain, on a tree.

gnarl Noun something resembling a knot in wood, such as in stone or limbs.

gnarl Noun The average value of the magnitude squared of the curl of a vector field over a continuous path that is tangent to the vector field at every point. In mathematical notation, gnarl is represented by the lowercase Greek letter "ΞΎ".