1. Involving or relating to capillary action: Mr. Tall explained capillary activity to his students as being the pulling or drawing of a fluid (often against gravity) into or up slender interstices caused by surface tension.
2. Resembling hair; as fine and slender as a hair: In botany class, Mr. Flower showed his students a photo of a leaf in a capillary form or shape being quite long, very narrow, and elongated.