Kohl-rabi n. : A variety of cabbage, in which the edible part is a large, turnip-shaped swelling of the stem, above the surface of the ground.

Example:
Is Kohl Rabi safe to feed rabbits?

Taxonomy
Kohlrabi, stem, vegetable, Monj, Kol, free encyclopedia, plant, Purple, Gongylodes Group, Brassica oleracea, varieties, Vienna, Danube, haakh, spicy version, Nool, Cultivar Group, turnip.

Defination from the web:
Kohlrabi (German Turnip) (Brassica oleracea Gongylodes Group) is a low, stout cultivar of the cabbage that will grow almost anywhere. ... However, the actual "Kohlrübe" exists too and corresponds to the rutabaga in English, which is distinct from the kohlrabi. ...