A substance possessing a peculiar rough austere taste. This is remarkable in the tincture of galls, bark, the husks of walnuts, green tea, port wine, etc. Leguin first observed that the astringent principle might be separated from the tincture of galls by albumen, with which it forms an insoluble compound. Astringents are sometimes called tannin, and are extensively employed in tanning leather. Astringents are used in medicine to relieve diarrhoea, and as tonics.