In 2007, the state of Oklahoma shook the produce world with controversy when it declared that watermelon was, in fact, a vegetable — not just any vegetable, though.
The Oklahoma House of Representatives declared watermelon the official state vegetable. Senator Don Barrington stated this was "because it's a member of the cucumber family."
While Barrington’s statement simplified the matter a bit, he wasn’t wrong. Watermelon is part of the gourd family, which also includes cucumbers, pumpkins, and squash.
Therefore, watermelons do meet the broadest definition of a vegetable, which refers to almost any harvested part of a plant.
However, the term "fruit" derives from the seed-bearing products of flowering plants, which makes a strong argument for watermelon being a fruit.