deal n.

交易；买卖；

She got a new car for $1000! That was really a good deal!

她一千美金买了辆车！真是捡了个大便宜！

a big deal

①重要的事情

He got promoted last month. That was a big deal to him!

他上个月升职了。这对他来说是个大事。

②重要的人物

I was kind of a big deal in high school.

高中时候我可是风云人物。

③有什么大不了的！（表示不屑）

A: Hey. I could do one-arm push-ups.

喂，我能做单手俯卧撑.

B: Big deal! I can do push-ups without using my hands!

有什么大不了！我可以不用手做！

deal in

经营；做… 的生意

My dad deals in medical supplies these days, selling X-ray and MRI machines to hospitals.

我爸爸做医疗用品的生意，就是往医院卖X光和核磁共振的一些设备。