n. A small knot or lump in thread, whether woven into cloth or not.n. A knot or an excrescence on walnut and other trees, used for ornamental veneering.To pick knots, loose threads, etc., from, as in finishing cloth; specifically, to pick (wool) by hand.To cleanse (cloth), as with fullers' earth or a similar substance.To welter.n. A pimple.Same as birl.