A misclick took me to the fruit tag, which has the definition:
Refers to the culinary definition of fruit: a sweet seed-containing part of a plant that is commonly eaten raw.
That seems like a hybrid of a botanical and a culinary definition.
Aside from the fact that seedless fruits are common (bananas anyone?), it would seem odd to exclude cooking apples, Seville oranges, and elderberries (botanically fruit, must be cooked due to toxins). Even lemons are at odds with this definition, as they're not "commonly eaten raw".
Rhubarb is almost invariably used as a fruit in the kitchen¹. Certainly I would expect to tag a question about rhubarb pie with [fruit][pie] as these cook rather differently to meat pies (for example).
Wikipedia in its list of culinary fruits uses a slightly different definition:
"Any sweet, edible part of a plant that resembles fruit, even if it does not develop from a floral ovary; also used in a technically imprecise sense for some sweet or sweetish vegetables, some of which may resemble a true fruit or are used in cookery as if they were a fruit, for example rhubarb."
(their quotes, I assume from the cited source Harri Vainio; Franca Bianchini (2003). Fruit and Vegetables. IARC. p. 2. ISBN 9283230086. but p.2 isn't viewable online).
I suggest we adopt similar terminology, especially dropping the raw part which seems uncommon elsewhere.
¹ If I get a good crop this year I intend to try making rhubarb chutney; chutneys of course are often made from fruit despite being savoury.