slippery elm, Large-leaved elm (Ulmus rubra or U. fulva) of eastern North America that has hard wood and fragrant inner bark. A gluelike substance in the inner bark has long been steeped in water as a remedy for throat ailments, powdered for use in poultices, and chewed as a thirst quencher, among other uses. It has received renewed attention in recent years as part of alternative medicine’s herbal pharmacopoeia, prescribed for a wide variety of ailments.