A common English name given by Chinese restaurants to a vegetarian dish (sometines Buddhist delight, as well). It refers to the fact that Buddhist monks in China and related countries were vegetarian, and would have to eat vegetarian dishes. So strong was the belief in vegetarianism among Chinese Buddhists that some scriptures in the tradition depict the Buddha as a vegetarian, despite the fact that many older scriptures (such as the Pali Canon) make it clear that the Buddha ate meat, and forbade the establishment of vegetarianism among the Sangha.
While there was actually quite a lot of good and fairly complex vegetarian cuisine served among Buddhists (monks and otherwise) in China, adaptation to Western tastes (and the greater availability of quality, cheap meat in the U.S. and elsewhere) means that often some variation on "Buddha's Delight" may be the only vegetarian dish available in Chinese restaurants outside of areas with large, well established Chinese communities. Typically, it consists primarily of stir fried vegetables (snow peas, carrots, peppers, cabbage (oriental or otherwise), onions, etc.) in a soy sauce based sauce, served over rice or noodles. What's that you say? Sound like no more than that staple of American Chinese cooking, chop suey, with the meat yanked out? Well, frankly, that's usually what it is.
For a fuller treatment of vegetarian eating among Buddhists in China, see the Buddhist vegetarians node.