Real Dictionary

vegetable
countable noun: Vegetables are plants such as cabbages, potatoes, and onions which you can cook and eat.

vegetable in American English
of, or having the nature of, plants in general
adjective: of, consisting of, or made from edible vegetables
noun: any plant whose fruit, seeds, roots, tubers, bulbs, stems, leaves, or flower parts are used as food, as the tomato, bean, beet, potato, onion, asparagus, spinach, or cauliflower

vegetable in British English
noun: any of various herbaceous plants having parts that are used as food, such as peas, beans, cabbage, potatoes, cauliflower, and onions