Prickly ash (Bot.), a prickly shrub (Xanthoxylum Americanum) with yellowish flowers appearing with the leaves. All parts of the plant are pungent and aromatic. The southern species is X. Carolinianum. Gray. -- Prickly heat (Med.), a noncontagious cutaneous eruption of red pimples, attended with intense itching and tingling of the parts affected. It is due to inflammation of the sweat glands, and is often brought on by overheating the skin in hot weather. -- Prickly pear (Bot.), a name given to several plants of the cactaceous genus Opuntia, American plants consisting of fleshy, leafless, usually flattened, and often prickly joints inserted upon each other. The sessile flowers have many petals and numerous stamens. The edible fruit is a large pear-shaped berry containing many flattish seeds. The common species of the Northern Atlantic States is Opuntia vulgaris. In the South and West are many others, and in tropical America more than a hundred more. O. vulgaris, O. Ficus-Indica, and O. Tuna are abundantly introduced in the Mediterranean region, and O. Dillenii has become common in India. -- Prickly pole (Bot.), a West Indian palm (Bactris Plumierana), the slender trunk of which bears many rings of long black prickles. -- Prickly withe (Bot.), a West Indian cactaceous plant (Cereus triangularis) having prickly, slender, climbing, triangular stems. -- Prickly rat (Zoöl.), any one of several species of South American burrowing rodents belonging to Ctenomys and allied genera. The hair is usually intermingled with sharp spines.