A plant raised for some edible part of it, such as the leaves, roots, fruit or flowers, but excluding any plant considered to be a fruit, grain, herb, or spice in the culinary sense, and usually including non-plants lumped into the same culinary category, such as edible mushrooms and seaweed.

https://en.wiktionary.org/wiki/vegetable

usually herbaceous plant (such as the cabbage, bean, or potato) grown for an edible part that is usually eaten as part of a meal

https://www.merriam-webster.com/dictionary/vegetable

it may include savoury fruits such as tomatoes and squash, flowers such as broccoli, and seeds such as pulses, but exclude foods derived from some plants that are fruits, flowers, nuts, and cereal grains.

https://en.wikipedia.org/wiki/Vegetable

I have never used dictionary.com but it's so full of adds that it's hard for me to take it seriously