Oolong (烏龍 wu1 long2 in the Mandarin Pinyin romanization) is a traditional Chinese type of tea somewhere in between green and black in oxidation (traditionally but improperly called "fermentation") time.
The term "oolong" means "black dragon" or "black snake" in Chinese; various legends describe the origin of this curious name. In one legend, the owner of a tea plantation was scared away from his drying tea leaves by the appearance of a black snake; when he cautiously returned several days later, the leaves had been oxidized by the sun and gave a delightful brew.
Oolong tea leaves are bruised after picking and left to oxidize in the sun, though not as long as leaves intended for black tea. Oolong tea contains more caffeine than green tea, but less than black. Tea connoisseurs classify the tea by its aroma (often fragrant or flowery), taste and aftertaste (often melony). The finest oolong tea in the word arguably comes from Formosa. Dong Ding (凍頂, in Pinyin dong4 ding3) Oolong (grown on Dong Ding mountain in Nan Tou, Taiwan) and Te Kwan Yin (鐵觀音, in Pinyin tie3 guan1 yin1) from Fujian province in China are considered premium grade Oolong tea.