Definitions
1.nounAny plant of the genus Rheum, especially Rheum rhabarbarum, having large leaves and long green or reddish acidic leafstalks that are edible, in particular when cooked (although the leaves are mildly poisonous).
2.nounThe leafstalks of common rhubarb or garden rhubarb (usually known as Rheum × hybridum), which are long, fleshy, often pale red, and with a tart taste, used as a food ingredient; they are frequently stewed with sugar and made into jam or used in crumbles, pies, etc.
3.nounThe dried rhizome and roots of Rheum palmatum (Chinese rhubarb) or Rheum officinale (Tibetan rhubarb), from China, used as a laxative and purgative.
4.nounA Royal Air Force World War II code name for operations by aircraft (fighters and fighter-bombers) involving low-level flight to seek opportunistic targets.
5.verbOf fighter aircraft: to fire at a target opportunistically.
6.adjectiveOf the colour of rhubarb: either brownish-yellow (the colour of rhubarb rhizomes and roots used for medicinal purposes), or pale red (often the colour of the leafstalks of common rhubarb).