(informal)be very knowledgeable about something(非正式)（在某方面）知識淵博的
柯林斯高階英漢雙解學習詞典釋義
N-VAR
洋蔥；洋蔥頭
An onion is a round vegetable with a brown skin that grows underground. It has many white layers on its inside which have a strong, sharp smell and taste.
例句
Will you chop an onion up for me?...你能幫我把一個洋蔥切碎嗎？It is made with fresh minced meat, cooked with onion and a rich tomato sauce.這道菜用鮮肉沫加洋蔥和濃郁的番茄醬做成。
英漢詞典釋義
n.
洋蔥(頭)
We grow onions in the garden.我們在園子里種洋蔥。
(食物)洋蔥, 蔥頭
There is too much onion in the salad.色拉中洋蔥太多。
英英詞典釋義
Noun
1. edible bulb of an onion plant
2. bulbous plant having hollow leaves cultivated worldwide for its rounded edible bulb