thinning noun 3adjective 1forms 3 noun3 •Process of removing plants or parts of plants to facilitate the growth of other plantsThe trimming, pruning and thinning must be managed with care. Some need more thinning than others. — 1881 •The action or result of reducing thickness, density, or numberIt is highly likely that this thinning was not atrophic or pathological, but simply the thinning from stretching under the forces of labor, as Bandl and others explain it. — 1885 •Wood, leaves, or other plant parts removed during the process of thinning adjective1 •Becoming less thick, dense, or numerous formsthinnings · more thinning · most thinning