cucumber

noun3

1. •
   The edible fruit of this plant, having a green rind and crisp white flesh.

   • […]for it has been a common saying of physicians in England, that a cucumber should be well sliced, and dressed with pepper and vinegar, and then thrown out, as good for nothing. — 1785
2. •
   A vine in the gourd family, Cucumis sativus.
3. •
   (informal, figurative) A person who is calm and self-possessed.

   • The guy's a real cucumber. — 1999