Longman Dictionary of Contemporary English
Douglas Harper's Etymology Dictionary
type of Chinese cabbage, from Cantonese, literally "white vegetable."
Wiktionary
n. Chinese cabbage, (taxlink Brassica rapa chinensis subspecies noshow=1), an East Asian leafy vegetable related to the Western cabbage.
WordNet
Wikipedia
Bok choy or pak choi (; Brassica rapa subsp. chinensis) is a type of Chinese cabbage. Chinensis varieties do not form heads; instead, they have smooth, dark green leaf blades forming a cluster reminiscent of mustard or celery. Chinensis varieties are popular in southern China and Southeast Asia. Being winter-hardy, they are increasingly grown in Northern Europe. This group was originally classified as its own species under the name Brassica chinensis by Linnaeus.
Usage examples of "bok choy".
All of them were tossed together in a flurry of bok choy and bamboo shoots, one smothered in a sauce that looked like Orange Crush thickened with cornstarch.