a long vegetable with dark green skin that is light green inside, usually eaten raw 黄瓜 
Word Originlate Middle English: from Old French cocombre, coucombre, from Latin cucumis, cucumer-.
Idioms
(as) cool as a cucumber
very calm and showing control, especially in a difficult situation （尤指在困难情况下）非常冷静，泰然自若 George is cool as a cucumber and this should be just another operation for him. 乔治的黄瓜很酷，这对他来说应该只是另一种手术。